Secure processor architecture for use with a digital rights management (drm) system on a computing device

ABSTRACT

A secure processor is operable in normal and preferred modes, and includes a security kernel instantiated when the processor enters into preferred mode and a security key accessible by the security kernel during preferred mode. The security kernel employs the accessed security key to authenticate a secure application, and allows the processor to be trusted to keep hidden a secret of the application. To instantiate the application, the processor enters preferred mode where the security key is accessible, and instantiates and runs the security kernel. The security kernel accesses the security key and applies same to decrypt a key for the application, stores the decrypted key in a location where the application will expect same, and instantiates the application. The processor then enters the normal mode, where the security key is not accessible.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.09/892,329, filed Jun. 27, 2001, which is related to U.S. patentapplication Ser. No. 09/290,363, filed Apr. 12, 1999 and entitled“ENFORCEMENT ARCHITECTURE AND METHOD FOR DIGITAL RIGHTS MANAGEMENT”, andU.S. Provisional Application No. 60/126,614, filed Mar. 27, 1999 andentitled “ENFORCEMENT ARCHITECTURE AND METHOD FOR DIGITAL RIGHTSMANAGEMENT”, each of which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to an architecture for enforcing rights indigital content. More specifically, the present invention relates tosuch an enforcement architecture that allows access to encrypted digitalcontent only in accordance with parameters specified by license rightsacquired by a user of the digital content. Even more specifically, thepresent invention relates to an architecture for a secure processor on acomputing device having a digital rights management (DRM) systemthereon.

BACKGROUND OF THE INVENTION

Digital rights management and enforcement is highly desirable inconnection with digital content such as digital audio, digital video,digital text, digital data, digital multimedia, etc., where such digitalcontent is to be distributed to users. Typical modes of distributioninclude tangible devices such as a magnetic (floppy) disk, a magnetictape, an optical (compact) disk (CD), etc., and intangible media such asan electronic bulletin board, an electronic network, the Internet, etc.Upon being received by the user, such user renders or ‘plays’ thedigital content with the aid of an appropriate rendering device such asa media player on a personal computer or the like.

Typically, a content owner or rights-owner, such as an author, apublisher, a broadcaster, etc. (hereinafter “content owner”), wishes todistribute such digital content to a user or recipient in exchange for alicense fee or some other consideration. Such content owner, given thechoice, would likely wish to restrict what the user can do with suchdistributed digital content. For example, the content owner would liketo restrict the user from copying and re-distributing such content to asecond user, at least in a manner that denies the content owner alicense fee from such second user.

In addition, the content owner may wish to provide the user with theflexibility to purchase different types of use licenses at differentlicense fees, while at the same time holding the user to the terms ofwhatever type of license is in fact purchased. For example, the contentowner may wish to allow distributed digital content to be played only alimited number of times, only for a certain total time, only on acertain type of machine, only on a certain type of media player, only bya certain type of user, etc.

However, after distribution has occurred, such content owner has verylittle if any control over the digital content. This is especiallyproblematic in view of the fact that practically every new or recentpersonal computer includes the software and hardware necessary to makean exact digital copy of such digital content, and to download suchexact digital copy to a writeable magnetic or optical disk, or to sendsuch exact digital copy over a network such as the Internet to anydestination.

Of course, as part of the legitimate transaction where the license feewas obtained, the content owner may require the user of the digitalcontent to promise not to re-distribute such digital content. However,such a promise is easily made and easily broken. A content owner mayattempt to prevent such re-distribution through any of several knownsecurity devices, usually involving encryption and decryption. However,there is likely very little that prevents a mildly determined user fromdecrypting encrypted digital content, saving such digital content in anun-encrypted form, and then re-distributing same.

A need exists, then, for providing an enforcement architecture andmethod that allows the controlled rendering or playing of arbitraryforms of digital content, where such control is flexible and definableby the content owner of such digital content. A need also exists forproviding a controlled rendering environment on a computing device suchas a personal computer, where the rendering environment includes atleast a portion of such enforcement architecture. Such controlledrendering environment allows that the digital content will only berendered as specified by the content owner, even though the digitalcontent is to be rendered on a computing device which is not under thecontrol of the content owner.

Further, a need exists for a trusted component running on the computingdevice, where the trusted component enforces the rights of the contentowner on such computing device in connection with a piece of digitalcontent, even against attempts by the user of such computing device toaccess such digital content in ways not permitted by the content owner.As but one example, such a trusted software component prevents a user ofthe computing device from making a copy of such digital content, exceptas otherwise allowed for by the content owner thereof.

Finally, a need exists for a secure processor and an architecturetherefor that can be trusted to keep hidden a secret of the trustedcomponent, especially in cases where the processor is on a portabledevice or the like.

SUMMARY OF THE INVENTION

The aforementioned needs are satisfied at least in part by anenforcement architecture and method for digital rights management, wherethe architecture and method enforce rights in protected (secure) digitalcontent available on a medium such as the Internet, an optical disk,etc. For purposes of making content available, the architecture includesa content server from which the digital content is accessible over theInternet or the like in an encrypted form. The content server may alsosupply the encrypted digital content for recording on an optical disk orthe like, wherein the encrypted digital content may be distributed onthe optical disk itself. At the content server, the digital content isencrypted using an encryption key, and public/private key techniques areemployed to bind the digital content with a digital license at theuser's computing device or client machine.

When a user attempts to render the digital content on a computingdevice, the rendering application invokes a Digital Rights Management(DRM) system on such user's computing device. If the user is attemptingto render the digital content for the first time, the DRM system eitherdirects the user to a license server to obtain a license to render suchdigital content in the manner sought, or transparently obtains suchlicense from such license server without any action necessary on thepart of the user. The license includes:

a decryption key (KD) that decrypts the encrypted digital content;

a description of the rights (play, copy, etc.) conferred by the licenseand related conditions (begin date, expiration date, number of plays,etc.), where such description is in a digitally readable form; and

a digital signature that ensures the integrity of the license.

The user should not be able to decrypt and render the encrypted digitalcontent without obtaining such a license from the license server. Theobtained license is stored in a license store in the user's computingdevice.

Importantly, the license server only issues a license to a DRM systemthat is ‘trusted’ (i.e., that can authenticate itself). To implement‘trust’, the DRM system is equipped with a ‘black box’ that performsdecryption and encryption functions for such DRM system. The black boxincludes a public/private key pair, a version number and a uniquesignature, all as provided by an approved certifying authority. Thepublic key is made available to the license server for purposes ofencrypting portions of the issued license, thereby binding such licenseto such black box. The private key is available to the black box only,and not to the user or anyone else, for purposes of decryptinginformation encrypted with the corresponding public key. The DRM systemis initially provided with a black box with a public/private key pair,and the user is prompted to download from a black box server an updatedsecure black box when the user first requests a license. The black boxserver provides the updated black box, along with a uniquepublic/private key pair. Such updated black box is written in uniqueexecutable code that will run only on the user's computing device, andis re-updated on a regular basis.

When a user requests a license, the client machine sends the black boxpublic key, version number, and signature to the license server, andsuch license server issues a license only if the version number iscurrent and the signature is valid. A license request also includes anidentification of the digital content for which a license is requestedand a key ID that identifies the decryption key associated with therequested digital content. The license server uses the black box publickey to encrypt the decryption key, and the decryption key to encrypt thelicense terms, then downloads the encrypted decryption key and encryptedlicense terms to the user's computing device along with a licensesignature.

Once the downloaded license has been stored in the DRM system licensestore, the user can render the digital content according to the rightsconferred by the license and specified in the license terms. When arequest is made to render the digital content, the black box is causedto decrypt the decryption key and license terms, and a DRM systemlicense evaluator evaluates such license terms. The black box decryptsthe encrypted digital content only if the license evaluation results ina decision that the requestor is allowed to play such content. Thedecrypted content is provided to the rendering application forrendering.

In the present invention, a secure processor for a computing device isoperable in a normal mode and a preferred mode, and includes a securitykernel for being instantiated on the processor when the processor entersinto the preferred mode and a security key accessible by theinstantiated security kernel when the processor is operating in thepreferred mode. The security kernel employs the accessed security keyduring the preferred mode to authenticate a secure application on thecomputing device, and allows the processor to be trusted to keep hiddena secret of the application.

To instantiate the secure application, the processor enters thepreferred mode where the security key is accessible, and instantiatesand runs the security kernel. The security kernel accesses the securitykey and applies same to decrypt at least one encrypted key for theapplication, stores the decrypted key(s) in a location where theapplication will expect the key(s) to be found, and instantiates and/orauthenticates the application on the processor. The processor thenenters the normal mode from the preferred mode, where the security keyis not accessible, and passes control to the application.

To instantiate one of a plurality of available secure applications, achooser value is set to a value corresponding to a chooser applicationupon power-up, preferred mode is entered upon a power-up CPU reset, andthe instantiated security kernel determines that the chooser valuecorresponds to the chooser application and therefore instantiates same.After the chooser application is instantiated and left to run, normalmode is entered and the chooser application presents the plurality ofavailable applications for selection by a user.

A selection of one of the presented applications to be instantiated isreceived, the chooser value is set to a value corresponding to theselected application, preferred mode is entered upon an executed CPUreset, and the instantiated security kernel determines that the chooservalue corresponds to the selected application and thereforeinstantiating same. After the selected application is instantiated andleft to run, normal mode is entered.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe embodiments of the present invention, will be better understood whenread in conjunction with the appended drawings. For the purpose ofillustrating the invention, there are shown in the drawings embodimentswhich are presently preferred. As should be understood, however, theinvention is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1 is a block diagram showing an enforcement architecture inaccordance with one embodiment of the present invention;

FIG. 2 is a block diagram of the authoring tool of the architecture ofFIG. 1 in accordance with one embodiment of the present invention;

FIG. 3 is a block diagram of a digital content package having digitalcontent for use in connection with the architecture of FIG. 1 inaccordance with one embodiment of the present invention;

FIG. 4 is a block diagram of the user's computing device of FIG. 1 inaccordance with one embodiment of the present invention;

FIGS. 5A and 5B are flow diagrams showing the steps performed inconnection with the Digital Rights Management (DRM) system of thecomputing device of FIG. 4 to render content in accordance with oneembodiment of the present invention;

FIG. 6 is a flow diagram showing the steps performed in connection withthe DRM system of FIG. 4 to determine whether any valid, enablinglicenses are present in accordance with one embodiment of the presentinvention;

FIG. 7 is a flow diagram showing the steps performed in connection withthe DRM system of FIG. 4 to obtain a license in accordance with oneembodiment of the present invention;

FIG. 8 is a block diagram of a digital license for use in connectionwith the architecture of FIG. 1 in accordance with one embodiment of thepresent invention;

FIG. 9 is a flow diagram showing the steps performed in connection withthe DRM system of FIG. 4 to obtain a new black box in accordance withone embodiment of the present invention;

FIG. 10 is a flow diagram showing the key transaction steps performed inconnection with the DRM system of FIG. 4 to validate a license and apiece of digital content and render the content in accordance with oneembodiment of the present invention;

FIG. 11 is a block diagram showing the license evaluator of FIG. 4 alongwith a Digital Rights License (DRL) of a license and a language enginefor interpreting the DRL in accordance with one embodiment of thepresent invention;

FIG. 12 is a block diagram representing a general purpose computersystem in which aspects of the present invention and/or portions thereofmay be incorporated;

FIG. 13 is a block diagram showing a portable device coupled to acomputer for downloading digital content and a digital license from thecomputer, where the portable device has a processor that runs a securekernel in accordance with one embodiment of the present invention;

FIG. 14 is a flow diagram showing steps performed by the processor andsecure kernel of the portable device of FIG. 13 in loading anapplication in accordance with one embodiment of the present invention;

FIG. 15 is a flow diagram showing steps performed by the processor andsecure kernel of the portable device of FIG. 13 in choosing anapplication to be loaded in accordance with one embodiment of thepresent invention;

FIG. 16 is a block diagram showing a code image of an application to beloaded by the security kernel of FIG. 13 in accordance with oneembodiment of the present invention where the security kernel employssymmetric cryptography;

FIG. 17 is a flow diagram showing steps performed by the security kernelof FIG. 16 in accordance with one embodiment of the present invention;

FIG. 18 is a flow diagram showing steps performed by a manufacturer ofthe portable device in one embodiment of the present invention where thesecurity kernel employs symmetric cryptography;

FIG. 19 is a block diagram showing a code image of an application to beloaded by the security kernel of FIG. 13 in accordance with oneembodiment of the present invention where the security kernel employsasymmetric cryptography;

FIG. 20 is a flow diagram showing steps performed by the security kernelof FIG. 19 in accordance with one embodiment of the present invention;and

FIG. 21 is a block diagram showing a code security kernel employingsymmetric cryptography instantiating an extended security kernelemploying asymmetric cryptography, which in turn instantiates anapplication in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings in details, wherein like numerals are used toindicate like elements throughout, there is shown in FIG. 1 anenforcement architecture 10 in accordance with one embodiment of thepresent invention. Overall, the enforcement architecture 10 allows anowner of digital content 12 to specify license rules that must besatisfied before such digital content 12 is allowed to be rendered on auser's computing device 14. Such license rules are embodied within adigital license 16 that the user/user's computing device 14(hereinafter, such terms are interchangeable unless circumstancesrequire otherwise) must obtain from the content owner or an agentthereof. The digital content 12 is distributed in an encrypted form, andmay be distributed freely and widely. Preferably, the decrypting key(KD) for decrypting the digital content 12 is included with the license16.

Computer Environment

FIG. 12 and the following discussion are intended to provide a briefgeneral description of a suitable computing environment in which thepresent invention and/or portions thereof may be implemented. Althoughnot required, the invention is described in the general context ofcomputer-executable instructions, such as program modules, beingexecuted by a computer, such as a client workstation or a server.Generally, program modules include routines, programs, objects,components, data structures and the like that perform particular tasksor implement particular abstract data types. Moreover, it should beappreciated that the invention and/or portions thereof may be practicedwith other computer system configurations, including hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network PCs, minicomputers, mainframe computers and thelike. The invention may also be practiced in distributed computingenvironments where tasks are performed by remote processing devices thatare linked through a communications network. In a distributed computingenvironment, program modules may be located in both local and remotememory storage devices.

As shown in FIG. 12, an exemplary general purpose computing systemincludes a conventional personal computer 120 or the like, including aprocessing unit 121, a system memory 122, and a system bus 123 thatcouples various system components including the system memory to theprocessing unit 121. The system bus 123 may be any of several types ofbus structures including a memory bus or memory controller, a peripheralbus, and a local bus using any of a variety of bus architectures. Thesystem memory includes read-only memory (ROM) 124 and random accessmemory (RAM) 125. A basic input/output system 126 (BIOS), containing thebasic routines that help to transfer information between elements withinthe personal computer 120, such as during start-up, is stored in ROM124.

The personal computer 120 may further include a hard disk drive 127 forreading from and writing to a hard disk (not shown), a magnetic diskdrive 128 for reading from or writing to a removable magnetic disk 129,and an optical disk drive 130 for reading from or writing to a removableoptical disk 131 such as a CD-ROM or other optical media. The hard diskdrive 127, magnetic disk drive 128, and optical disk drive 130 areconnected to the system bus 123 by a hard disk drive interface 132, amagnetic disk drive interface 133, and an optical drive interface 134,respectively. The drives and their associated computer-readable mediaprovide non-volatile storage of computer readable instructions, datastructures, program modules and other data for the personal computer 20.

Although the exemplary environment described herein employs a hard disk,a removable magnetic disk 129, and a removable optical disk 131, itshould be appreciated that other types of computer readable media whichcan store data that is accessible by a computer may also be used in theexemplary operating environment. Such other types of media include amagnetic cassette, a flash memory card, a digital video disk, aBernoulli cartridge, a random access memory (RAM), a read-only memory(ROM), and the like.

A number of program modules may be stored on the hard disk, magneticdisk 129, optical disk 131, ROM 124 or RAM 125, including an operatingsystem 135, one or more application programs 136, other program modules137 and program data 138. A user may enter commands and information intothe personal computer 120 through input devices such as a keyboard 140and pointing device 142. Other input devices (not shown) may include amicrophone, joystick, game pad, satellite disk, scanner, or the like.These and other input devices are often connected to the processing unit121 through a serial port interface 146 that is coupled to the systembus, but may be connected by other interfaces, such as a parallel port,game port, or universal serial bus (USB). A monitor 147 or other type ofdisplay device is also connected to the system bus 123 via an interface,such as a video adapter 148. In addition to the monitor 147, a personalcomputer typically includes other peripheral output devices (not shown),such as speakers and printers. The exemplary system of FIG. 12 alsoincludes a host adapter 155, a Small Computer System Interface (SCSI)bus 156, and an external storage device 162 connected to the SCSI bus156.

The personal computer 120 may operate in a networked environment usinglogical connections to one or more remote computers, such as a remotecomputer 149. The remote computer 149 may be another personal computer,a server, a router, a network PC, a peer device or other common networknode, and typically includes many or all of the elements described aboverelative to the personal computer 120, although only a memory storagedevice 150 has been illustrated in FIG. 12. The logical connectionsdepicted in FIG. 12 include a local area network (LAN) 151 and a widearea network (WAN) 152. Such networking environments are commonplace inoffices, enterprise-wide computer networks, intranets, and the Internet.

When used in a LAN networking environment, the personal computer 120 isconnected to the LAN 151 through a network interface or adapter 153.When used in a WAN networking environment, the personal computer 120typically includes a modem 154 or other means for establishingcommunications over the wide area network 152, such as the Internet. Themodem 154, which may be internal or external, is connected to the systembus 123 via the serial port interface 146. In a networked environment,program modules depicted relative to the personal computer 120, orportions thereof, may be stored in the remote memory storage device. Itwill be appreciated that the network connections shown are exemplary andother means of establishing a communications link between the computersmay be used.

Architecture

Referring again to FIG. 1, in one embodiment of the present invention,the architecture 10 includes an authoring tool 18, a content-keydatabase 20, a content server 22, a license server 24, and a black boxserver 26, as well as the aforementioned user's computing device 14.

Architecture—Authoring Tool 18

The authoring tool 18 is employed by a content owner to package a pieceof digital content 12 into a form that is amenable for use in connectionwith the architecture 10 of the present invention. In particular, thecontent owner provides the authoring tool 18 with the digital content12, instructions and/or rules that are to accompany the digital content12, and instructions and/or rules as to how the digital content 12 is tobe packaged. The authoring tool 18 then produces a digital contentpackage 12 p having the digital content 12 encrypted according to anencryption/decryption key, and the instructions and/or rules thataccompany the digital content 12.

In one embodiment of the present invention, the authoring tool 18 isinstructed to serially produce several different digital content 12packages 12 p, each having the same digital content 12 encryptedaccording to a different encryption/decryption key. As should beunderstood, having several different packages 12 p with the same digitalcontent 12 may be useful for tracking the distribution of such packages12 p/content 12 (hereinafter simply “digital content 12”, unlesscircumstances require otherwise). Such distribution tracking is notordinarily necessary, but may be used by an investigative authority incases where the digital content 12 has been illegally sold or broadcast.

In one embodiment of the present invention, the encryption/decryptionkey that encrypts the digital content 12 is a symmetric key, in that theencryption key is also the decryption key (KD). As will be discussedbelow in more detail, such decryption key (KD) is delivered to a user'scomputing device 14 in a hidden form as part of a license 16 for suchdigital content 12. Preferably, each piece of digital content 12 isprovided with a content ID (or each package 12 p is provided with apackage ID), each decryption key (KD) has a key ID, and the authoringtool 18 causes the decryption key (KD), key ID, and content ID (orpackage ID) for each piece of digital content 12 (or each package 12 p)to be stored in the content-key database 20. In addition, license dataregarding the types of licenses 16 to be issued for the digital content12 and the terms and conditions for each type of license 16 may bestored in the content-key database 20, or else in another database (notshown). Preferably, the license data can be modified by the contentowner at a later time as circumstances and market conditions mayrequire.

In use, the authoring tool 18 is supplied with information including,among other things:

the digital content 12 to be packaged;

the type and parameters of watermarking and/or fingerprinting to beemployed, if any;

the type and parameters of data compression to be employed, if any;

the type and parameters of encryption to be employed;

the type and parameters of serialization to be employed, if any; and

the instructions and/or rules that are to accompany the digital content12.

As is known, a watermark is a hidden, computer-readable signal that isadded to the digital content 12 as an identifier. A fingerprint is awatermark that is different for each instance. As should be understood,an instance is a version of the digital content 12 that is unique.Multiple copies of any instance may be made, and any copy is of aparticular instance. When a specific instance of digital content 12 isillegally sold or broadcast, an investigative authority can perhapsidentify suspects according to the watermark/fingerprint added to suchdigital content 12.

Data compression may be performed according to any appropriatecompression algorithm without departing from the spirit and scope of thepresent invention. For example, the .mp3 or .wav compression algorithmmay be employed. Of course, the digital content 12 may already be in acompressed state, in which case no additional compression is necessary.

The instructions and/or rules that are to accompany the digital content12 may include practically any appropriate instructions, rules, or otherinformation without departing from the spirit and scope of the presentinvention. As will be discussed below, such accompanyinginstructions/rules/information are primarily employed by the user andthe user's computing device 14 to obtain a license 16 to render thedigital content 12. Accordingly, such accompanyinginstructions/rules/information may include an appropriately formattedlicense acquisition script or the like, as will be described in moredetail below. In addition, or in the alternative, such accompanyinginstructions/rules/information may include ‘preview’ informationdesigned to provide a user with a preview of the digital content 12.

With the supplied information, the authoring tool 18 then produces oneor more packages 12 p corresponding to the digital content 12. Eachpackage 12 p may then be stored on the content server 22 fordistribution to the world.

In one embodiment of the present invention, and referring now to FIG. 2,the authoring tool 18 is a dynamic authoring tool 18 that receives inputparameters which can be specified and operated on. Accordingly, suchauthoring tool 18 can rapidly produce multiple variations of package 12p for multiple pieces of digital content 12. Preferably, the inputparameters are embodied in the form of a dictionary 28, as shown, wherethe dictionary 28 includes such parameters as:

the name of the input file 29 a having the digital content 12;

the type of encoding that is to take place

the encryption/decryption key (KD) to be employed,

the accompanying instructions/rules/information (‘header information’)to be packaged with the digital content 12 in the package 12 p.

the type of muxing that is to occur; and

the name of the output file 29 b to which the package 12 p based on thedigital content 12 is to be written.

As should be understood, such dictionary 28 is easily and quicklymodifiable by an operator of the authoring tool 18 (human or machine),and therefore the type of authoring performed by the authoring tool 18is likewise easily and quickly modifiable in a dynamic manner. In oneembodiment of the present invention, the authoring tool 18 includes anoperator interface (not shown) displayable on a computer screen to ahuman operator. Accordingly, such operator may modify the dictionary 28by way of the interface, and further may be appropriately aided and/orrestricted in modifying the dictionary 28 by way of the interface.

In the authoring tool 18, and as seen in FIG. 2, a source filter 18 areceives the name of the input file 29 a having the digital content 12from the dictionary 28, and retrieves such digital content 12 from suchinput file and places the digital content 12 into a memory 29 c such asa RAM or the like. An encoding filter 18 b then performs encoding on thedigital content 12 in the memory 29 c to transfer the file from theinput format to the output format according to the type of encodingspecified in the dictionary 28 (i.e., .wav to .asp, .mp3 to .asp, etc.),and places the encoded digital content 12 in the memory 29 c. As shown,the digital content 12 to be packaged (music, e.g.) is received in acompressed format such as the .wav or .mp3 format, and is transformedinto a format such as the .asp (active streaming protocol) format. Ofcourse, other input and output formats may be employed without departingfrom the spirit and scope of the present invention.

Thereafter, an encryption filter 18 c encrypts the encoded digitalcontent 12 in the memory 29 c according to the encryption/decryption key(KD) specified in the dictionary 28, and places the encrypted digitalcontent 12 in the memory 29 c. A header filter 18 d then adds the headerinformation specified in the dictionary 28 to the encrypted digitalcontent 12 in the memory 29 c.

As should be understood, depending on the situation, the package 12 pmay include multiple streams of temporally aligned digital content 12(one stream being shown in FIG. 2), where such multiple streams aremultiplexed (i.e., ‘muxed’). Accordingly, a mux filter 18 e performsmuxing on the header information and encrypted digital content 12 in thememory 29 c according to the type of muxing specified in the dictionary28, and places the result in the memory 29 c. A file writer filter 18 fthen retrieves the result from the memory 29 c and writes such result tothe output file 29 b specified in the dictionary 28 as the package 12 p.

It should be noted that in certain circumstances, the type of encodingto be performed will not normally change. Since the type of muxingtypically is based on the type of encoding, it is likewise the case thatthe type of muxing will not normally change, either. If this is in factthe case, the dictionary 28 need not include parameters on the type ofencoding and/or the type of muxing. Instead, it is only necessary thatthe type of encoding be ‘hardwired’ into the encoding filter and/or thatthe type of muxing be ‘hardwired’ into the mux filter. Of course, ascircumstance require, the authoring tool 18 may not include all of theaforementioned filters, or may include other filters, and any includedfilter may be hardwired or may perform its function according toparameters specified in the dictionary 28, all without departing fromthe spirit and scope of the present invention.

Preferably, the authoring tool 18 is implemented on an appropriatecomputer, processor, or other computing machine by way of appropriatesoftware. The structure and operation of such machine and such softwareshould be apparent based on the disclosure herein and therefore do notrequire any detailed discussion in the present disclosure.

Architecture—Content Server 22

Referring again to FIG. 1, in one embodiment of the present invention,the content server 22 distributes or otherwise makes available forretrieval the packages 12 p produced by the authoring tool 18. Suchpackages 12 p may be distributed as requested by the content server 22by way of any appropriate distribution channel without departing fromthe spirit and scope of the present invention. For example, suchdistribution channel may be the Internet or another network, anelectronic bulletin board, electronic mail, or the like. In addition,the content server 22 may be employed to copy the packages 12 p ontomagnetic or optical disks or other storage devices, and such storagedevices may then be distributed.

It will be appreciated that the content server 22 distributes packages12 p without regard to any trust or security issues. As discussed below,such issues are dealt with in connection with the license server 24 andthe relationship between such license server 24 and the user's computingdevice 14. In one embodiment of the present invention, the contentserver 22 freely releases and distributes packages 12 p having digitalcontent 12 to any distributes requesting same. However, the contentserver 22 may also release and distribute such packages 12 p in arestricted manner without departing from the spirit and scope of thepresent invention. For example, the content server 22 may first requirepayment of a pre-determined distribution fee prior to distribution, ormay require that a distributee identify itself, or may indeed make adetermination of whether distribution is to occur based on anidentification of the distributee.

In addition, the content server 22 may be employed to perform inventorymanagement by controlling the authoring tool 18 to generate a number ofdifferent packages 12 p in advance to meet an anticipated demand. Forexample, the server could generate 100 packages 12 p based on the samedigital content 12, and serve each package 12 p 10 times. As supplies ofpackages 12 p dwindle to 20, for example, the content server 22 may thendirect the authoring tool 18 to generate 80 additional packages 12 p,again for example.

Preferably, the content server 22 in the architecture 10 has a uniquepublic/private key pair (PU-CS, PR-CS) that is employed as part of theprocess of evaluating a license 16 and obtaining a decryption key (KD)for decrypting corresponding digital content 12, as will be explained inmore detail below. As is known, a public/private key pair is anasymmetric key, in that what is encrypted in one of the keys in the keypair can only be decrypted by the other of the keys in the key pair. Ina public/private key pair encryption system, the public key may be madeknown to the world, but the private key should always be held inconfidence by the owner of such private key. Accordingly, if the contentserver 22 encrypts data with its private key (PR-CS), it can send theencrypted data out into the world with its public key (PU-CS) fordecryption purposes. Correspondingly, if an external device wants tosend data to the content server 22 so that only such content server 22can decrypt such data, such external device must first obtain the publickey of the content server 22 (PU-CS) and then must encrypt the data withsuch public key. Accordingly, the content server 22 (and only thecontent server 22) can then employ its private key (PR-CS) to decryptsuch encrypted data.

As with the authoring tool 18, the content server 22 is implemented onan appropriate computer, processor, or other computing machine by way ofappropriate software. The structure and operation of such machine andsuch software should be apparent based on the disclosure herein andtherefore do not require any detailed discussion in the presentdisclosure. Moreover, in one embodiment of the present invention, theauthoring tool 18 and the content server 22 may reside on a singlecomputer, processor, or other computing machine, each in a separate workspace. It should be recognized, moreover, that the content server 22 mayin certain circumstances include the authoring tool 18 and/or performthe functions of the authoring tool 18, as discussed above.

Structure of Digital Content Package 12 p

Referring now to FIG. 3, in one embodiment of the present invention, thedigital content package 12 p as distributed by the content server 22includes:

the digital content 12 encrypted with the encryption/decryption key(KD), as was discussed above (i.e., (KD(CONTENT)));

the content ID (or package ID) of such digital content 12 (or package 12p);

the key ID of the decryption key (KD);

license acquisition information, preferably in an un-encrypted form; and

the key KD encrypting the content server 22 public key (PU-CS), signedby the content server 22 private key (PR-CS) (i.e., (KD (PU-CS) S(PR-CS))).

With regard to (KD (PU-CS) S (PR-CS)), it is to be understood that suchitem is to be used in connection with validating the digital content 12and/or package 12 p, as will be explained below. Unlike a certificatewith a digital signature (see below), the key (PU-CS) is not necessaryto get at (KD (PU-CS)). Instead, the key (PU-CS) is obtained merely byapplying the decryption key (KD). Once so obtained, such key (PU-CS) maybe employed to test the validity of the signature (S (PR-CS)).

It should also be understood that for such package 12 p to beconstructed by the authoring tool 18, such authoring tool 18 mustalready possess the license acquisition information and (KD (PU-CS) S(PR-CS)), presumably as header information supplied by the dictionary28. Moreover, the authoring tool 18 and the content server 22 mustpresumably interact to construct (KD (PU-CS) S (PR-CS)). Suchinteraction may for example include the steps of:

the content server 22 sending (PU-CS) to the authoring tool 18;

the authoring tool 18 encrypting (PU-CS) with (KD) to produce (KD(PU-CS));

the authoring tool 18 sending (KD (PU-CS)) to the content server 22;

the content server 22 signing (KD (PU-CS)) with (PR-CS) to produce (KD(PU-CS) S (PR-CS)); and

the content server 22 sending (KD (PU-CS) S (PR-CS)) to the authoringtool 18.

Architecture—License Server 24

Referring again to FIG. 1, in one embodiment of the present invention,the license server 24 performs the functions of receiving a request fora license 16 from a user's computing device 14 in connection with apiece of digital content 12, determining whether the user's computingdevice 14 can be trusted to honor an issued license 16, negotiating sucha license 16, constructing such license 16, and transmitting suchlicense 16 to the user's computing device 14. Preferably, suchtransmitted license 16 includes the decryption key (KD) for decryptingthe digital content 12. Such license server 24 and such functions willbe explained in more detail below. Preferably, and like the contentserver 22, the license server 24 in the architecture 10 has a uniquepublic/private key pair (PU-LS, PR-LS) that is employed as part of theprocess of evaluating a license 16 and obtaining a decryption key (KD)for decrypting corresponding digital content 12, as will be explained inmore detail below.

As with the authoring tool 18 and the content server 22, the licenseserver 24 is implemented on an appropriate computer, processor, or othercomputing machine by way of appropriate software. The structure andoperation of such machine and such software should be apparent based onthe disclosure herein and therefore do not require any detaileddiscussion in the present disclosure. Moreover, in one embodiment of thepresent invention the authoring tool 18 and/or the content server 22 mayreside on a single computer, processor, or other computing machinetogether with the license server 24, each in a separate work space.

In one embodiment of the present invention, prior to issuance of alicense 16, the license server 24 and the content server 22 enter intoan agency agreement or the like, wherein the license server 24 in effectagrees to be the licensing authority for at least a portion of thedigital content 12 distributed by the content server 22. As should beunderstood, one content server 22 may enter into an agency agreement orthe like with several license servers 24, and/or one license server 24may enter into an agency agreement or the like with several contentservers 22, all without departing from the spirit and scope of thepresent invention.

Preferably, the license server 24 can show to the world that it does infact have the authority to issue a license 16 for digital content 12distributed by the content server 22. To do so, it is preferable thatthe license server 24 send to the content server 22 the license server24 public key (PU-LS), and that the content server 22 then send to thelicense server 24 a digital certificate containing PU-LS as the contentssigned by the content server 22 private key (CERT (PU-LS) S (PR-CS)). Asshould be understood, the contents (PU-LS) in such certificate can onlybe accessed with the content server 22 public key (PU-CS). As shouldalso be understood, in general, a digital signature of underlying datais an encrypted form of such data, and will not match such data whendecrypted if such data has been adulterated or otherwise modified.

As a licensing authority in connection with a piece of digital content12, and as part of the licensing function, the license server 24 musthave access to the decryption key (KD) for such digital content 12.Accordingly, it is preferable that license server 24 have access to thecontent-key database 20 that has the decryption key (KD), key ID, andcontent ID (or package ID) for such digital content 12 (or package 12p).

Architecture—Black Box Server 26

Still referring to FIG. 1, in one embodiment of the present invention,the black box server 26 performs the functions of installing and/orupgrading a new black box 30 in a user's computing device 14. As will beexplained in more detail below, the black box 30 performs encryption anddecryption functions for the user's computing device 14. As will also beexplained in more detail below, the black box 30 is intended to besecure and protected from attack. Such security and protection isprovided, at least in part, by upgrading the black box 30 to a newversion as necessary by way of the black box server 26, as will beexplained in more detail below.

As with the authoring tool 18, the content server 22, and the licenseserver 24, the black box server 26 is implemented on an appropriatecomputer, processor, or other computing machine by way of appropriatesoftware. The structure and operation of such machine and such softwareshould be apparent based on the disclosure herein and therefore do notrequire any detailed discussion in the present disclosure. Moreover, inone embodiment of the present invention the license server 24, theauthoring tool 18, and/or the content server 22 may reside on a singlecomputer, processor, or other computing machine together with the blackbox server 26, each in a separate work space. Note, though, that forsecurity purposes, it may be wise to have the black box server 26 on aseparate machine.

Architecture—User's Computing Device 14

Referring now to FIG. 4, in one embodiment of the present invention, theuser's computing device 14 is a personal computer or the like, havingelements including a keyboard, a mouse, a screen, a processor, RAM, ROM,a hard drive, a floppy drive, a CD player, and/or the like. However, theuser's computing device 14 may also be a dedicated viewing device suchas a television or monitor, a dedicated audio device such as a stereo orother music player, a dedicated printer, or the like, among otherthings, all without departing from the spirit and scope of the presentinvention.

The content owner for a piece of digital content 12 must trust that theuser's computing device 14 will abide by the rules specified by suchcontent owner, i.e. that the digital content 12 will not be renderedunless the user obtains a license 16 that permits the rendering in themanner sought. Preferably, then, the user's computing device 14 mustprovide a trusted component or mechanism 32 that can satisfy to thecontent owner that such computing device 14 will not render the digitalcontent 12 except according to the license rules embodied in the license16 associated with the digital content 12 and obtained by the user.

Here, the trusted mechanism 32 is a Digital Rights Management (DRM)system 32 that is enabled when a user requests that a piece of digitalcontent 12 be rendered, that determines whether the user has a license16 to render the digital content 12 in the manner sought, thateffectuates obtaining such a license 16 if necessary, that determineswhether the user has the right to play the digital content 12 accordingto the license 16, and that decrypts the digital content 12 forrendering purposes if in fact the user has such right according to suchlicense 16. The contents and function of the DRM system 32 on the user'scomputing device 14 and in connection with the architecture 10 aredescribed below.

DRM System 32

The DRM system 32 performs four main functions with the architecture 10disclosed herein: (1) content acquisition, (2) license acquisition, (3)content rendering, and (4) black box 30 installation/update. Preferably,any of the functions can be performed at any time, although it isrecognized that some of the functions already require that digitalcontent 12 be acquired.

DRM System 32—Content Acquisition

Acquisition of digital content 12 by a user and/or the user's computingdevice 14 is typically a relatively straight-forward matter andgenerally involves placing a file having encrypted digital content 12 onthe user's computing device 14. Of course, to work with the architecture10 and the DRM system 32 disclosed herein, it is necessary that theencrypted digital content 12 be in a form that is amenable to sucharchitecture 10 and DRM system 32, such as the digital package 12 p aswill be described below.

As should be understood, the digital content 12 may be obtained in anymanner from a content server 22, either directly or indirectly, withoutdeparting from the spirit and scope of the present invention. Forexample, such digital content 12 may be downloaded from a network suchas the Internet, located on an obtained optical or magnetic disk or thelike, received as part of an E-mail message or the like, or downloadedfrom an electronic bulletin board or the like.

Such digital content 12, once obtained, is preferably stored in a mannersuch that the obtained digital content 12 is accessible by a renderingapplication 34 (to be described below) running on the computing device14, and by the DRM system 32. For example, the digital content 12 may beplaced as a file on a hard drive (not shown) of the user's computingdevice 14, or on a network server (not shown) accessible to thecomputing device 14. In the case where the digital content 12 isobtained on an optical or magnetic disk or the like, it may only benecessary that such disk be present in an appropriate drive (not shown)coupled to the user's computing device 14.

In the present invention, it is not envisioned that any special toolsare necessary to acquire digital content 12, either from the contentserver 22 as a direct distribution source or from some intermediary asan indirect distribution source. That is, it is preferable that digitalcontent 12 be as easily acquired as any other data file. However, theDRM system 32 and/or the rendering application 34 may include aninterface (not shown) designed to assist the user in obtaining digitalcontent 12. For example, the interface may include a web browserespecially designed to search for digital content 12, links topre-defined Internet web sites that are known to be sources of digitalcontent 12, and the like.

DRM System 32—Content Rendering, Part 1

Referring now to FIG. 5A, in one embodiment of the present invention,assuming the encrypted digital content 12 has been distributed to andreceived by a user and placed by the user on the computing device 14 inthe form of a stored file, the user will attempt to render the digitalcontent 12 by executing some variation on a render command (step 501).For example, such render command may be embodied as a request to ‘play’or ‘open’ the digital content 12. In some computing environments, suchas for example the “MICROSOFT WINDOWS”operating system, distributed byMICROSOFT Corporation of Redmond, Wash., such play or open command maybe as simple as ‘clicking’ on an icon representative of the digitalcontent 12. Of course, other embodiments of such render command may beemployed without departing from the spirit and scope of the presentinvention. In general, such render command may be considered to beexecuted whenever a user directs that a file having digital content 12be opened, run, executed, and/or the like.

Importantly, and in addition, such render command may be embodied as arequest to copy the digital content 12 to another form, such as to aprinted form, a visual form, an audio form, etc. As should beunderstood, the same digital content 12 may be rendered in one form,such as on a computer screen, and then in another form, such as aprinted document. In the present invention, each type of rendering isperformed only if the user has the right to do so, as will be explainedbelow.

In one embodiment of the present invention, the digital content 12 is inthe form of a digital file having a file name ending with an extension,and the computing device 14 can determine based on such extension tostart a particular kind of rendering application 34. For example, if thefile name extension indicates that the digital content 12 is a textfile, the rendering application 34 is some form of word processor suchas the “MICROSOFT WORD”, distributed by MICROSOFT Corporation ofRedmond, Wash. Likewise, if the file name extension indicates that thedigital content 12 is an audio, video, and/or multimedia file, therendering application 34 is some form of multimedia player, such as“MICROSOFT MEDIA PLAYER”, also distributed by MICROSOFT Corporation ofRedmond, Wash.

Of course, other methods of determining a rendering application may beemployed without departing from the spirit and scope of the presentinvention. As but one example, the digital content 12 may containmeta-data in an un-encrypted form (i.e., the aforementioned headerinformation), where the meta-data includes information on the type ofrendering application 34 necessary to render such digital content 12.

Preferably, such rendering application 34 examines the digital content12 associated with the file name and determines whether such digitalcontent 12 is encrypted in a rights-protected form (steps 503, 505). Ifnot protected, the digital content 12 may be rendered without furtherado (step 507). If protected, the rendering application 34 determinesfrom the encrypted digital content 12 that the DRM system 32 isnecessary to play such digital content 12. Accordingly, such renderingapplication 34 directs the user's computing device 14 to run the DRMsystem 32 thereon (step 509). Such rendering application 34 then callssuch DRM system 32 to decrypt the digital content 12 (step 511). As willbe discussed in more detail below, the DRM system 32 in fact decryptsthe digital content 12 only if the user has a valid license 16 for suchdigital content 12 and the right to play the digital content 12according to the license rules in the valid license 16. Preferably, oncethe DRM system 32 has been called by the rendering application 34, suchDRM system 32 assumes control from the rendering application 34, atleast for purposes of determining whether the user has a right to playsuch digital content 12 (step 513).

DRM System 32 Components

In one embodiment of the present invention, and referring again to FIG.4, the DRM system 32 includes a license evaluator 36, the black box 30,a license store 38, and a state store 40.

DRM System 32 Components—License Evaluator 36

The license evaluator 36 locates one or more licenses 16 that correspondto the requested digital content 12, determines whether such licenses 16are valid, reviews the license rules in such valid licenses 16, anddetermines based on the reviewed license rules whether the requestinguser has the right to render the requested digital content 12 in themanner sought, among other things. As should be understood, the licenseevaluator 36 is a trusted component in the DRM system 32. In the presentdisclosure, to be ‘trusted’ means that the license server 24 (or anyother trusting element) is satisfied that the trusted element will carryout the wishes of the owner of the digital content 12 according to therights description in the license 16, and that a user cannot easilyalter such trusted element for any purpose, nefarious or otherwise.

The license evaluator 36 has to be trusted in order to ensure that suchlicense evaluator 36 will in fact evaluate a license 16 properly, and toensure that such license evaluator 36 has not been adulterated orotherwise modified by a user for the purpose of bypassing actualevaluation of a license 16. Accordingly, the license evaluator 36 is runin a protected or shrouded environment such that the user is deniedaccess to such license evaluator 36. Other protective measures may ofcourse be employed in connection with the license evaluator 36 withoutdeparting from the spirit and scope of the present invention.

DRM System 32 Components—Black Box 30

Primarily, and as was discussed above, the black box 30 performsencryption and decryption functions in the DRM system 32. In particular,the black box 30 works in conjunction with the license evaluator 36 todecrypt and encrypt certain information as part of the licenseevaluation function. In addition, once the license evaluator 36determines that a user does in fact have the right to render therequested digital content 12 in the manner sought, the black box 30 isprovided with a decryption key (KD) for such digital content 12, andperforms the function of decrypting such digital content 12 based onsuch decryption key (KD).

The black box 30 is also a trusted component in the DRM system 32. Inparticular, the license server 24 must trust that the black box 30 willperform the decryption function only in accordance with the licenserules in the license 16, and also trust that such black box 30 will notoperate should it become adulterated or otherwise modified by a user forthe nefarious purpose of bypassing actual evaluation of a license 16.Accordingly, the black box 30 is also run in a protected or shroudedenvironment such that the user is denied access to such black box 30.Again, other protective measures may be employed in connection with theblack box 30 without departing from the spirit and scope of the presentinvention. Preferably, and like the content server 22 and license server24, the black box 30 in the DRM system 32 has a unique public/privatekey pair (PU-BB, PR-BB) that is employed as part of the process ofevaluating the license 16 and obtaining a decryption key (KD) fordecrypting the digital content 12, as will be described in more detailbelow.

DRM System 32 Components—License Store 38

The license store 38 stores licenses 16 received by the DRM system 32for corresponding digital content 12. The license store 38 itself neednot be trusted since the license store 38 merely stores licenses 16,each of which already has trust components built thereinto, as will bedescribed below. In one embodiment of the present invention, the licensestore 38 is merely a sub-directory of a drive such as a hard disk driveor a network drive. However, the license store 38 may be embodied in anyother form without departing from the spirit and scope of the presentinvention, so long as such license store 38 performs the function ofstoring licenses 16 in a location relatively convenient to the DRMsystem 32.

DRM System 32 Components—State Store 40

The state store 40 performs the function of maintaining stateinformation corresponding to licenses 16 presently or formerly in thelicense store 38. Such state information is created by the DRM system 32and stored in the state store 40 as necessary. For example, if aparticular license 16 only allows a pre-determined number of renderingsof a piece of corresponding digital content 12, the state store 40maintains state information on how many renderings have in fact takenplace in connection with such license 16. The state store 40 continuesto maintain state information on licenses 16 that are no longer in thelicense store 38 to avoid the situation where it would otherwise beadvantageous to delete a license 16 from the license store 38 and thenobtain an identical license 16 in an attempt to delete the correspondingstate information from the state store 40.

The state store 40 also has to be trusted in order to ensure that theinformation stored therein is not reset to a state more favorable to auser. Accordingly, the state store 40 is likewise run in a protected orshrouded environment such that the user is denied access to such statestore 40. Once again, other protective measures may of course beemployed in connection with the state store 40 without departing fromthe spirit and scope of the present invention. For example, the statestore 40 may be stored by the DRM system 32 on the computing device 14in an encrypted form.

DRM System 32—Content Rendering, Part 2

Referring again to FIG. 5A, and again discussing content rendering inone embodiment of the present invention, once the DRM system 32 hasassumed control from the calling rendering application 34, such DRMsystem 32 then begins the process of determining whether the user has aright to render the requested digital content 12 in the manner sought.In particular, the DRM system 32 either locates a valid, enablinglicense 16 in the license store (steps 515, 517) or attempts to acquirea valid, enabling license 16 from the license server 24 (i.e. performsthe license acquisition function as discussed below and as shown in FIG.7).

As a first step, and referring now to FIG. 6, the license evaluator 36of such DRM system 32 checks the license store 38 for the presence ofone or more received licenses 16 that correspond to the digital content12 (step 601). Typically, the license 16 is in the form of a digitalfile, as will be discussed below, although it will be recognized thatthe license 16 may also be in other forms without departing from thespirit and scope of the present invention. Typically, the user willreceive the digital content 12 without such license 16, although it willlikewise be recognized that the digital content 12 may be received witha corresponding license 16 without departing from the spirit and scopeof the present invention.

As was discussed above in connection with FIG. 3, each piece of digitalcontent 12 is in a package 12 p with a content ID (or package ID)identifying such digital content 12 (or package 12 p), and a key IDidentifying the decryption key (KD) that will decrypt the encrypteddigital content 12. Preferably, the content ID (or package ID) and thekey ID are in an un-encrypted form. Accordingly, and in particular,based on the content ID of the digital content 12, the license evaluator36 looks for any license 16 in the license store 38 that contains anidentification of applicability to such content ID. Note that multiplesuch licenses 16 may be found, especially if the owner of the digitalcontent 12 has specified several different kinds of licenses 16 for suchdigital content 12, and the user has obtained multiple ones of suchlicenses 16. If in fact the license evaluator 36 does not find in thelicense store 38 any license 16 corresponding to the requested digitalcontent 12, the DRM system 32 may then perform the function of licenseacquisition (step 519 of FIG. 5), to be described below.

Assume now that the DRM system 32 has been requested to render a pieceof digital content 12, and one or more licenses 16 corresponding theretoare present in the license store 38. In one embodiment of the presentinvention, then, the license evaluator 36 of the DRM system 32 proceedsto determine for each such license 16 whether such license 16 itself isvalid (steps 603 and 605 of FIG. 6). Preferably, and in particular, eachlicense 16 includes a digital signature 26 based on the content 28 ofthe license 16. As should be understood, the digital signature 26 willnot match the license 16 if the content 28 has been adulterated orotherwise modified. Thus, the license evaluator 36 can determine basedon the digital signature 26 whether the content 28 is in the form thatit was received from the license server 24 (i.e., is valid). If no validlicense 16 is found in the license store 38, the DRM system 32 may thenperform the license acquisition function described below to obtain sucha valid license 16.

Assuming that one or more valid licenses 16 are found, for each validlicense 16, the license evaluator 36 of the DRM system 32 nextdetermines whether such valid license 16 gives the user the right torender the corresponding digital content 12 in the manner desired (i.e.,is enabling) (steps 607 and 609). In particular, the license evaluator36 determines whether the requesting user has the right to play therequested digital content 12 based on the rights description in eachlicense 16 and based on what the user is attempting to do with thedigital content 12. For example, such rights description may allow theuser to render the digital content 12 into a sound, but not into adecrypted digital copy.

As should be understood, the rights description in each license 16specifies whether the user has rights to play the digital content 12based on any of several factors, including who the user is, where theuser is located, what type of computing device 14 the user is using,what rendering application 34 is calling the DRM system 32, the date,the time, etc. In addition, the rights description may limit the license16 to a pre-determined number of plays, or pre-determined play time, forexample. In such case, the DRM system 32 must refer to any stateinformation with regard to the license 16, (i.e., how many times thedigital content 12 has been rendered, the total amount of time thedigital content 12 has been rendered, etc.), where such stateinformation is stored in the state store 40 of the DRM system 32 on theuser's computing device 14.

Accordingly, the license evaluator 36 of the DRM system 32 reviews therights description of each valid license 16 to determine whether suchvalid license 16 confers the rights sought to the user. In doing so, thelicense evaluator 36 may have to refer to other data local to the user'scomputing device 14 to perform a determination of whether the user hasthe rights sought. As seen in FIG. 4, such data may include anidentification 42 of the user's computing device (machine) 14 andparticular aspects thereof, an identification 44 of the user andparticular aspects thereof, an identification of the renderingapplication 34 and particular aspects thereof, a system clock 46, andthe like. If no valid license 16 is found that provides the user withthe right to render the digital content 12 in the manner sought, the DRMsystem 32 may then perform the license acquisition function describedbelow to obtain such a license 16, if in fact such a license 16 isobtainable.

Of course, in some instances the user cannot obtain the right to renderthe digital content 12 in the manner requested, because the contentowner of such digital content 12 has in effect directed that such rightnot be granted. For example, the content owner of such digital content12 may have directed that no license 16 be granted to allow a user toprint a text document, or to copy a multimedia presentation into anun-encrypted form. In one embodiment of the present invention, thedigital content 12 includes data on what rights are available uponpurchase of a license 16, and types of licenses 16 available. However,it will be recognized that the content owner of a piece of digitalcontent 12 may at any time change the rights currently available forsuch digital content 12 by changing the licenses 16 available for suchdigital content 12.

DRM System 32—License Acquisition

Referring now to FIG. 7, if in fact the license evaluator 36 does notfind in the license store 38 any valid, enabling license 16corresponding to the requested digital content 12, the DRM system 32 maythen perform the function of license acquisition. As shown in FIG. 3,each piece of digital content 12 is packaged with information in anun-encrypted form regarding how to obtain a license 16 for renderingsuch digital content 12 (i.e., license acquisition information).

In one embodiment of the present invention, such license acquisitioninformation may include (among other things) types of licenses 16available, and one or more Internet web sites or other site informationat which one or more appropriate license servers 24 may be accessed,where each such license server 24 is in fact capable of issuing alicense 16 corresponding to the digital content 12. Of course, thelicense 16 may be obtained in other manners without departing from thespirit and scope of the present invention. For example, the license 16may be obtained from a license server 24 at an electronic bulletinboard, or even in person or via regular mail in the form of a file on amagnetic or optical disk or the like.

Assuming that the location for obtaining a license 16 is in fact alicense server 24 on a network, the license evaluator 36 thenestablishes a network connection to such license server 24 based on theweb site or other site information, and then sends a request for alicense 16 from such connected license server 24 (steps 701, 703). Inparticular, once the DRM system 32 has contacted the license server 24,such DRM system 32 transmits appropriate license request information 36to such license server 24. In one embodiment of the present invention,such license 16 request information 36 may include:

the public key of the black box 30 of the DRM system 32 (PU-BB);

the version number of the black box 30 of the DRM system 32;

a certificate with a digital signature from a certifying authoritycertifying the black box 30 (where the certificate may in fact includethe aforementioned public key and version number of the black box 30);

the content ID (or package ID) that identifies the digital content 12(or package 12 p);

the key ID that identifies the decryption key (KD) for decrypting thedigital content 12;

the type of license 16 requested (if in fact multiple types areavailable);

the type of rendering application 34 that requested rendering of thedigital content 12;

and/or the like, among other things. Of course, greater or lessoramounts of license 16 request information 36 may be transmitted to thelicense server 24 by the DRM system 32 without departing from the spiritand scope of the present invention. For example, information on the typeof rendering application 34 may not be necessary, while additionalinformation about the user and/or the user's computing device 14 may benecessary.

Once the license server 24 has received the license 16 requestinformation 36 from the DRM system 32, the license server 24 may thenperform several checks for trust/authentication and for other purposes.In one embodiment of the present invention, such license server 24checks the certificate with the digital signature of the certifyingauthority to determine whether such has been adulterated or otherwisemodified (steps 705, 707). If so, the license server 24 refuses to grantany license 16 based on the request information 36. The license server24 may also maintain a list of known ‘bad’ users and/or user's computingdevices 14, and may refuse to grant any license 16 based on a requestfrom any such bad user and/or bad user's computing device 14 on thelist. Such ‘bad’ list may be compiled in any appropriate manner withoutdeparting from the spirit and scope of the present invention.

Based on the received request and the information associated therewith,and particularly based on the content ID (or package ID) in the licenserequest information, the license server 24 can interrogate thecontent-key database 20 (FIG. 1) and locate a record corresponding tothe digital content 12 (or package 12 p) that is the basis of therequest. As was discussed above, such record contains the decryption key(KD), key ID, and content ID for such digital content 12. In addition,such record may contain license data regarding the types of licenses 16to be issued for the digital content 12 and the terms and conditions foreach type of license 16. Alternatively, such record may include apointer, link, or reference to a location having such additionalinformation.

As mentioned above, multiple types of licenses 16 may be available. Forexample, for a relatively small license fee, a license 16 allowing alimited number of renderings may be available. For a relatively greaterlicense fee, a license 16 allowing unlimited renderings until anexpiration date may be available. For a still greater license fee, alicense 16 allowing unlimited renderings without any expiration date maybe available. Practically any type of license 16 having any kind oflicense terms may be devised and issued by the license server 24 withoutdeparting from the spirit and scope of the present invention.

In one embodiment of the present invention, the request for a license 16is accomplished with the aid of a web page or the like as transmittedfrom the license server 24 to the user's computing device 14.Preferably, such web page includes information on all types of licenses16 available from the license server 24 for the digital content 12 thatis the basis of the license 16 request.

In one embodiment of the present invention, prior to issuing a license16, the license server 24 checks the version number of the black box 30to determine whether such black box 30 is relatively current (steps 709,711). As should be understood, the black box 30 is intended to be secureand protected from attacks from a user with nefarious purposes (i.e., toimproperly render digital content 12 without a license 16, or outsidethe terms of a corresponding license 16). However, it is to berecognized that no system and no software device is in fact totallysecure from such an attack.

As should also be understood, if the black box 30 is relatively current,i.e., has been obtained or updated relatively recently, it is lesslikely that such black box 30 has been successfully attacked by such anefarious user. Preferably, and as a matter of trust, if the licenseserver 24 receives a license request with request information 36including a black box 30 version number that is not relatively current,such license server 24 refuses to issue the requested license 16 untilthe corresponding black box 30 is upgraded to a current version, as willbe described below. Put simply, the license server 24 will not trustsuch black box 30 unless such black box 30 is relatively current.

In the context of the black box 30 of the present invention, the term‘current’ or ‘relatively current’ may have any appropriate meaningwithout departing from the spirit and scope of the present invention,consistent with the function of providing trust in the black box 30based on the age or use thereof. For example, ‘current’ may be definedaccording to age (i.e., less than one month old). As an alternativeexample, ‘current’ may be defined based on a number of times that theblack box 30 has decrypted digital content 12 (i.e., less than 200instances of decryption). Moreover, ‘current’ may be based on policy asset by each license server 24, where one license server 24 may define‘current’ differently from another license server 24, and a licenseserver 24 may further define ‘current’ differently depending on thedigital content 12 for which a license 16 is requested, or depending onthe type of license 16 requested, among other things.

Assuming that the license server 24 is satisfied from the version numberof a black box 30 or other indicia thereof that such black box 30 iscurrent, the license server 24 then proceeds to negotiate terms andconditions for the license 16 with the user (step 713). Alternatively,the license server 24 negotiates the license 16 with the user, thensatisfies itself from the version number of the black box 30 that suchblack box 30 is current (i.e., performs step 713, then step 711). Ofcourse, the amount of negotiation varies depending on the type oflicense 16 to be issued, and other factors. For example, if the licenseserver 24 is merely issuing a paid-up unlimited use license 16, verylittle need be negotiated. On the other hand, if the license 16 is to bebased on such items as varying values, sliding scales, break points, andother details, such items and details may need to be worked out betweenthe license server 24 and the user before the license 16 can be issued.

As should be understood, depending on the circumstances, the licensenegotiation may require that the user provide further information to thelicense server 24 (for example, information on the user, the user'scomputing device 14, etc.). Importantly, the license negotiation mayalso require that the user and the license server 24 determine amutually acceptable payment instrument (a credit account, a debitaccount, a mailed check, etc.) and/or payment method (paid-upimmediately, spread over a period of time, etc.), among other things.

Once all the terms of the license 16 have been negotiated and agreed toby both the license server 24 and user (step 715), a digital license 16is generated by the license server 24 (step 719), where such generatedlicense 16 is based at least in part on the license request, the blackbox 30 public key (PU-BB), and the decryption key (KD) for the digitalcontent 12 that is the basis of the request as obtained from thecontent-key database 20. In one embodiment of the present invention, andas seen in FIG. 8, the generated license 16 includes:

the content ID of the digital content 12 to which the license 16applies;

a Digital Rights License (DRL) 48 (i.e., the rights description oractual terms and conditions of the license 16 written in a predeterminedform that the license evaluator 36 can interrogate), perhaps encryptedwith the decryption key (KD) (i.e., KD (DRL));

the decryption key (KD) for the digital content 12 encrypted with theblack box 30 public key (PU-BB) as receive in the license request(i.e.,(PU-BB (KD));

a digital signature from the license server 24 (without any attachedcertificate) based on (KD (DRL)) and (PU-BB (KD)) and encrypted with thelicense server 24 private key (i.e., (S (PR-LS))); and

the certificate that the license server 24 obtained previously from thecontent server 22, such certificate indicating that the license server24 has the authority from the content server 22 to issue the license 16(i.e., (CERT (PU-LS) S (PR-CS))).

As should be understood, the aforementioned elements and perhaps othersare packaged into a digital file or some other appropriate form. Asshould also be understood, if the DRL 48 or (PU-BB (KD)) in the license16 should become adulterated or otherwise modified, the digitalsignature (S (PR-LS)) in the license 16 will not match and thereforewill not validate such license 16. For this reason, the DRL 48 need notnecessarily be in an encrypted form (i.e., (KD(DRL)) as mentionedabove), although such encrypted form may in some instances be desirableand therefore may be employed without departing from the spirit andscope of the present invention.

Once the digital license 16 has been prepared, such license 16 is thenissued to the requestor (i.e., the DRM system 32 on the user's computingdevice 14) (step 719 of FIG. 7). Preferably, the license 16 istransmitted over the same path through which the request therefor wasmade (i.e., the Internet or another network), although another path maybe employed without departing from the spirit and scope of the presentinvention. Upon receipt, the requesting DRM system 32 preferablyautomatically places the received digital license 16 in the licensestore 38 (step 721).

It is to be understood that a user's computing device 14 may on occasionmalfunction, and licenses 16 stored in the license store 38 of the DRMsystem 32 on such user's computing device 14 may become irretrievablylost. Accordingly, it is preferable that the license server 24 maintaina database 50 of issued licenses 16 (FIG. 1), and that such licenseserver 24 provide a user with a copy or re-issue (hereinafter‘re-issue’) of an issued license 16 if the user is in fact entitled tosuch re-issue. In the aforementioned case where licenses 16 areirretrievably lost, it is also likely the case that state informationstored in the state store 40 and corresponding to such licenses 16 isalso lost. Such lost state information should be taken into account whenre-issuing a license 16. For example, a fixed number of renderingslicense 16 might legitimately be re-issued in a pro-rated form after arelatively short period of time, and not re-issued at all after arelatively longer period of time.

DRM System 32—Installation/Upgrade of Black Box 30

As was discussed above, as part of the function of acquiring a license16, the license server 24 may deny a request for a license 16 from auser if the user's computing device 14 has a DRM system 32 with a blackbox 30 that is not relatively current, i.e., has a relatively oldversion number. In such case, it is preferable that the black box 30 ofsuch DRM system 32 be upgraded so that the license acquisition functioncan then proceed. Of course, the black box 30 may be upgraded at othertimes without departing from the spirit and scope of the presentinvention.

Preferably, as part of the process of installing the DRM system 32 on auser's computing device 14, a non-unique ‘lite’ version of a black box30 is provided. Such ‘lite’ black box 30 is then upgraded to a uniqueregular version prior to rendering a piece of digital content 12. Asshould be understood, if each black box 30 in each DRM system 32 isunique, a security breach into one black box 30 cannot easily bereplicated with any other black box 30.

Referring now to FIG. 9, the DRM system 32 obtains the unique black box30 by requesting same from a black box server 26 or the like (as wasdiscussed above and as shown in FIG. 1) (step 901). Typically, suchrequest is made by way of the Internet, although other means of accessmay be employed without departing from the spirit and scope of thepresent invention. For example, the connection to a black box server 26may be a direct connection, either locally or remotely. An upgrade fromone unique non-lite black box 30 to another unique non-lite black box 30may also be requested by the DRM system 32 at any time, such as forexample a time when a license server 24 deems the black box 30 notcurrent, as was discussed above.

Thereafter, the black box server 26 generates a new unique black box 30(step 903). As seen in FIG. 3, each new black box 30 is provided with aversion number and a certificate with a digital signature from acertifying authority. As was discussed above in connection with thelicense acquisition function, the version number of the black box 30indicates the relative age and/or use thereof. The certificate with thedigital signature from the certifying authority, also discussed above inconnection with the license acquisition function, is a proffer orvouching mechanism from the certifying authority that a license server24 should trust the black box 30. Of course, the license server 24 musttrust the certifying authority to issue such a certificate for a blackbox 30 that is in fact trustworthy. It may be the case, in fact, thatthe license server 24 does not trust a particular certifying authority,and refuses to honor any certificate issued by such certifyingauthority. Trust may not occur, for example, if a particular certifyingauthority is found to be engaging in a pattern of improperly issuingcertificates.

Preferably, and as was discussed above, the black box server 26 includesa new unique public/private key pair (PU-BB, PR-BB) with the newlygenerated unique black box 30 (step 903 of FIG. 9). Preferably, theprivate key for the black box 30 (PR-BB) is accessible only to suchblack box 30, and is hidden from and inaccessible by the remainder ofthe world, including the computing device 14 having the DRM system 32with such black box 30, and the user thereof.

Most any hiding scheme may be employed without departing from the spiritand scope of the present invention, so long as such hiding scheme infact performs the function of hiding the private key (PR-BB) from theworld. As but one example, the private key (PR-BB) may be split intoseveral sub-components, and each sub-component may be encrypted uniquelyand stored in a different location. In such a situation, it ispreferable that such sub-components are never assembled in full toproduce the entire private key (PR-BB).

In one embodiment of the present invention, such private key (PR-BB) isencrypted according to code-based encryption techniques. In particular,in such embodiment, the actual software code of the black box 30 (orother software code) is employed as encrypting key(s). Accordingly, ifthe code of the black box 30 (or the other software code) becomesadulterated or otherwise modified, for example by a user with nefariouspurposes, such private key (PR-BB) cannot be decrypted.

Although each new black box 30 is delivered with a new public/privatekey pair (PU-BB, PR-BB), such new black box 30 is also preferably givenaccess to old public/private key pairs from old black boxes 30previously delivered to the DRM system 32 on the user's computing device14 (step 905). Accordingly, the upgraded black box 30 can still employthe old key pairs to access older digital content 12 and oldercorresponding licenses 16 that were generated according to such old keypairs, as will be discussed in more detail below.

Preferably, the upgraded black box 30 delivered by the black box server26 is tightly tied to or associated with the user's computing device 14.Accordingly, the upgraded black box 30 cannot be operably transferredamong multiple computing devices 14 for nefarious purposes or otherwise.In one embodiment of the present invention, as part of the request forthe black box 30 (step 901) the DRM system 32 provides hardwareinformation unique to such DRM system 32 and/or unique to the user'scomputing device 14 to the black box server 26, and the black box server26 generates a black box 30 for the DRM system 32 based in part on suchprovided hardware information. Such generated upgraded black box 30 isthen delivered to and installed in the DRM system 32 on the user'scomputing device 14 (steps 907, 909). If the upgraded black box 30 isthen somehow transferred to another computing device 14, the transferredblack box 30 recognizes that it is not intended for such other computingdevice 14, and does not allow any requested rendering to proceed on suchother computing device 14.

Once the new black box 30 is installed in the DRM system 32, such DRMsystem 32 can proceed with a license acquisition function or with anyother function.

DRM System 32—Content Rendering, Part 3

Referring now to FIG. 5B, and assuming, now, that the license evaluator36 has found at least one valid license 16 and that at least one of suchvalid licenses 16 provides the user with the rights necessary to renderthe corresponding digital content 12 in the manner sought (i.e., isenabling), the license evaluator 36 then selects one of such licenses 16for further use (step 519). Specifically, to render the requesteddigital content 12, the license evaluator 36 and the black box 30 incombination obtain the decryption key (KD) from such license 16, and theblack box 30 employs such decryption key (KD) to decrypt the digitalcontent 12. In one embodiment of the present invention, and as wasdiscussed above, the decryption key (KD) as obtained from the license 16is encrypted with the black box 30 public key (PU-BB(KD)), and the blackbox 30 decrypts such encrypted decryption key with its private key(PR-BB) to produce the decryption key (KD) (steps 521, 523). However,other methods of obtaining the decryption key (KD) for the digitalcontent 12 may be employed without departing from the spirit and scopeof the present invention.

Once the black box 30 has the decryption key (KD) for the digitalcontent 12 and permission from the license evaluator 36 to render thedigital content 12, control may be returned to the rendering application34 (steps 525, 527). In one embodiment of the present invention, therendering application 34 then calls the DRM system 32/black box 30 anddirects at least a portion of the encrypted digital content 12 to theblack box 30 for decryption according to the decryption key (KD) (step529). The black box 30 decrypts the digital content 12 based upon thedecryption key (KD) for the digital content 12, and then the black box30 returns the decrypted digital content 12 to the rendering application34 for actual rendering (steps 533, 535). The rendering application 34may either send a portion of the encrypted digital content 12 or theentire digital content 12 to the black box 30 for decryption based onthe decryption key (KD) for such digital content 12 without departingfrom the spirit and scope of the present invention.

Preferably, when the rendering application 34 sends digital content 12to the black box 30 for decryption, the black box 30 and/or the DRMsystem 32 authenticates such rendering application 34 to ensure that itis in fact the same rendering application 34 that initially requestedthe DRM system 32 to run (step 531). Otherwise, the potential existsthat rendering approval may be obtained improperly by basing therendering request on one type of rendering application 34 and in factrendering with another type of rendering application 34. Assuming theauthentication is successful and the digital content 12 is decrypted bythe black box 30, the rendering application 34 may then render thedecrypted digital content 12 (steps 533, 535).

Sequence of Key Transactions

Referring now to FIG. 10, in one embodiment of the present invention, asequence of key transactions is performed to obtain the decryption key(KD) and evaluate a license 16 for a requested piece of digital content12 (i.e., to perform steps 515-523 of FIGS. 5A and 5B). Mainly, in suchsequence, the DRM system 32 obtains the decryption key (KD) from thelicense 16, uses information obtained from the license 16 and thedigital content 12 to authenticate or ensure the validity of both, andthen determines whether the license 16 in fact provides the right torender the digital content 12 in the manner sought. If so, the digitalcontent 12 may be rendered.

Bearing in mind that each license 16 for the digital content 12, as seenin FIG. 8, includes:

the content ID of the digital content 12 to which the license 16applies;

the Digital Rights License (DRL) 48, perhaps encrypted with thedecryption key (KD) (i.e., KD (DRL));

the decryption key (KD) for the digital content 12 encrypted with theblack box 30 public key (PU-BB) (i.e.,(PU-BB (KD));

the digital signature from the license server 24 based on (KD (DRL)) and(PU-BB (KD)) and encrypted with the license server 24 private key (i.e.,(S (PR-LS))); and

the certificate that the license server 24 obtained previously from thecontent server 22 (i.e., (CERT (PU-LS) S (PR-CS))),

and also bearing in mind that the package 12 p having the digitalcontent 12, as seen in FIG. 3, includes:

the content ID of such digital content 12;

the digital content 12 encrypted by KD (i.e., (KD(CONTENT)));

a license acquisition script that is not encrypted; and

the key KD encrypting the content server 22 public key (PU-CS), signedby the content server 22 private key (PR-CS) (i.e., (KD (PU-CS) S(PR-CS))),

In one embodiment of the present invention, the specific sequence of keytransactions that are performed with regard to a specific one of thelicenses 16 for the digital content 12 is as follows:

1. Based on (PU-BB (KD)) from the license 16, the black box 30 of theDRM system 32 on the user's computing device 14 applies its private key(PR-BB) to obtain (KD) (step 1001). (PR-BB (PU-BB (KD))=(KD)). Note,importantly, that the black box 30 could then proceed to employ KD todecrypt the digital content 12 without any further ado. However, andalso importantly, the license server 24 trusts the black box 30 not todo so. Such trust was established at the time such license server 24issued the license 16 based on the certificate from the certifyingauthority vouching for the trustworthiness of such black box 30.Accordingly, despite the black box 30 obtaining the decryption key (KD)as an initial step rather than a final step, the DRM system 32 continuesto perform all license 16 validation and evaluation functions, asdescribed below.

2. Based on (KD (PU-CS) S (PR-CS)) from the digital content 12, theblack box 30 applies the newly obtained decryption key (KD) to obtain(PU-CS) (step 1003). (KD (KD (PU-CS))=(PU-CS)). Additionally, the blackbox 30 can apply (PU-CS) as against the signature (S (PR-CS)) to satisfyitself that such signature and such digital content 12/ package 12 p isvalid (step 1005). If not valid, the process is halted and access to thedigital content 12 is denied.

3. Based on (CERT (PU-LS) S (PR-CS)) from the license 16, the black box30 applies the newly obtained content server 22 public key (PU-CS) tosatisfy itself that the certificate is valid (step 1007), signifyingthat the license server 24 that issued the license 16 had the authorityfrom the content server 22 to do so, and then examines the certificatecontents to obtain (PU-LS) (step 1009). If not valid, the process ishalted and access to the digital content 12 based on the license 16 isdenied.

4. Based on (S (PR-LS)) from the license 16, the black box 30 appliesthe newly obtained license server 24 public key (PU-LS) to satisfyitself that the license 16 is valid (step 1011). If not valid, theprocess is halted and access to the digital content 12 based on thelicense 16 is denied.

5. Assuming all validation steps are successful, and that the DRL 48 inthe license 16 is in fact encrypted with the decryption key (KD), thelicense evaluator 36 then applies the already-obtained decryption key(KD) to (KD(DRL)) as obtained from the license 16 to obtain the licenseterms from the license 16 (i.e., the DRL 48) (step 1013). Of course, ifthe DRL 48 in the license 16 is not in fact encrypted with thedecryption key (KD), step 1013 may be omitted. The license evaluator 36then evaluates/interrogates the DRL 48 and determines whether the user'scomputing device 14 has the right based on the DRL 48 in the license 16to render the corresponding digital content 12 in the manner sought(i.e., whether the DRL 48 is enabling) (step 1015). If the licenseevaluator 36 determines that such right does not exist, the process ishalted and access to the digital content 12 based on the license 16 isdenied.

6. Finally, assuming evaluation of the license 16 results in a positivedetermination that the user's computing device 14 has the right based onthe DRL 48 terms to render the corresponding digital content 12 in themanner sought, the license evaluator 36 informs the black box 30 thatsuch black box 30 can render the corresponding digital content 12according to the decryption key (KD). The black box 30 thereafterapplies the decryption key (KD) to decrypt the digital content 12 fromthe package 12 p (i.e., (KD(KD(CONTENT))=(CONTENT)) (step 1017).

It is important to note that the above-specified series of stepsrepresents an alternating or ‘ping-ponging’ between the license 16 andthe digital content 12. Such ping-ponging ensures that the digitalcontent 12 is tightly bound to the license 16, in that the validationand evaluation process can only occur if both the digital content 12 andlicense 16 are present in a properly issued and valid form. In addition,since the same decryption key (KD) is needed to get the content server22 public key (PU-CS) from the license 16 and the digital content 12from the package 12 p in a decrypted form (and perhaps the license terms(DRL 48) from the license 16 in a decrypted form), such items are alsotightly bound. Signature validation also ensures that the digitalcontent 12 and the license 16 are in the same form as issued from thecontent server 22 and the license server 24, respectively. Accordingly,it is difficult if not impossible to decrypt the digital content 12 bybypassing the license server 24, and also difficult if not impossible toalter and then decrypt the digital content 12 or the license 16.

In one embodiment of the present invention, signature verification, andespecially signature verification of the license 16, is alternatelyperformed as follows. Rather than having a signature encrypted by theprivate key of the license server 16 (PR-LS), as is seen in FIG. 8, eachlicense 16 has a signature encrypted by a private root key (PR-R) (notshown), where the black box 30 of each DRM system 32 includes a publicroot key (PU-R) (also not shown) corresponding to the private root key(PR-R). The private root key (PR-R) is known only to a root entity, anda license server 24 can only issue licenses 16 if such license server 24has arranged with the root entity to issue licenses 16.

In particular, in such embodiment:

1. the license server 24 provides its public key (PU-LS) to the rootentity;

2. the root entity returns the license server public key (PU-LS) to suchlicense server 24 encrypted with the private root key (PR-R) (i.e.,(CERT (PU-LS) S (PR-R))); and

3. the license server 24 then issues a license 16 with a signatureencrypted with the license server private key (S (PR-LS)), and alsoattaches to the license the certificate from the root entity (CERT(PU-LS) S (PR-R)).

For a DRM system 18 to validate such issued license 16, then, the DRMsystem 18:

1. applies the public root key (PU-R) to the attached certificate (CERT(PU-LS) S (PR-R)) to obtain the license server public key (PU-LS); and

2. applies the obtained license server public key (PU-LS) to thesignature of the license 16 (S (PR-LS).

Importantly, it should be recognized that just as the root entity gavethe license server 24 permission to issue licenses 16 by providing thecertificate (CERT (PU-LS) S (PR-R)) to such license server 24, suchlicense server 24 can provide a similar certificate to a second licenseserver 24 (i.e., (CERT (PU-LS2) S (PR-LS1)), thereby allowing the secondlicense server to also issue licenses 16. As should now be evident, alicense 16 issued by the second license server would include a firstcertificate (CERT (PU-LS1) S (PR-R)) and a second certificate (CERT(PU-LS2) S (PR-LS1)). Likewise, such license 16 is validated byfollowing the chain through the first and second certificates. Ofcourse, additional links in the chain may be added and traversed.

One advantage of the aforementioned signature verification process isthat the root entity may periodically change the private root key(PR-R), thereby likewise periodically requiring each license server 24to obtain a new certificate (CERT (PU-LS) S (PR-R)). Importantly, as arequirement for obtaining such new certificate, each license server maybe required to upgrade itself. As with the black box 30, if a licenseserver 24 is relatively current, i.e., has been upgraded relativelyrecently, it is less likely that license server 24 has been successfullyattacked. Accordingly, as a matter of trust, each license server 24 ispreferably required to be upgraded periodically via an appropriateupgrade trigger mechanism such as the signature verification process. Ofcourse, other upgrade mechanisms may be employed without departing fromthe spirit and scope of the present invention.

Of course, if the private root key (PR-R) is changed, then the publicroot key (PU-R) in each DRM system 18 must also be changed. Such changemay for example take place during a normal black box 30 upgrade, or infact may require that a black box 30 upgrade take place. Although achanged public root key (PU-R) may potentially interfere with signaturevalidation for an older license 16 issued based on an older private rootkey (PR-R), such interference may be minimized by requiring that anupgraded black box 30 remember all old public root keys (PU-R).Alternatively, such interference may be minimized by requiring signatureverification for a license 16 only once, for example the first time suchlicense 16 is evaluated by the license evaluator 36 of a DRM system 18.In such case, state information on whether signature verification hastaken place should be compiled, and such state information should bestored in the state store 40 of the DRM system 18.

Digital Rights License 48

In one embodiment of the present invention, the license evaluator 36evaluates a Digital Rights License (DRL) 48 as the rights description orterms of a license 16 to determine if such DRL 48 allows rendering of acorresponding piece of digital content 12 in the manner sought. In oneembodiment of the present invention, the DRL 48 may be written by alicensor (i.e., the content owner) in any DRL language.

As should be understood, there are a multitude of ways to specify a DRL48. Accordingly, a high degree of flexibility must be allowed for in anyDRL language. However, it is impractical to specify all aspects of a DRL48 in a particular license language, and it is highly unlikely that theauthor of such a language can appreciate all possible licensing aspectsthat a particular digital licensor may desire. Moreover, a highlysophisticated license language may be unnecessary and even a hindrancefor a licensor providing a relatively simple DRL 48. Nevertheless, alicensor should not be unnecessarily restricted in how to specify a DRL48. At the same time, the license evaluator 36 should always be able toget answers from a DRL 48 regarding a number of specific licensequestions.

In the present invention, and referring now to FIG. 11, a DRL 48 can bespecified in any license language, but includes a language identifier ortag 54. The license evaluator 36 evaluating the license 16, then,performs the preliminary step of reviewing the language tag 54 toidentify such language, and then selects an appropriate license languageengine 52 for accessing the license 16 in such identified language. Asshould be understood, such license language engine 52 must be presentand accessible to the license evaluator 36. If not present, the languagetag 54 and/or the DRL 48 preferably includes a location 56 (typically aweb site) for obtaining such language engine 52.

Typically, the language engine 52 is in the form of an executable fileor set of files that reside in a memory of the user's computing device14, such as a hard drive. The language engine 52 assists the licenseevaluator 36 to directly interrogate the DRL 48, the license evaluator36 interrogates the DRL 48 indirectly via the language engine 48 actingas an intermediary, or the like. When executed, the language engine 52runs in a work space in a memory of the user's computing device 14, suchas RAM. However, any other form of language engine 52 may be employedwithout departing from the spirit and scope of the present invention.

Preferably, any language engine 52 and any DRL language supports atleast a number of specific license questions that the license evaluator36 expects to be answered by any DRL 48, as will be discussed below.Accordingly, the license evaluator 36 is not tied to any particular DRLlanguage; a DRL 48 may be written in any appropriate DRL language; and aDRL 48 specified in a new license language can be employed by anexisting license evaluator 36 by having such license evaluator 36 obtaina corresponding new language engine 52.

DRL Languages

Two examples of DRL languages, as embodied in respective DRLs 48, areprovided below. The first, ‘simple’ DRL 48 is written in a DRL languagethat specifies license attributes, while the second ‘script’ DRL 48 iswritten in a DRL language that can perform functions according to thescript specified in the DRL 48. While written in a DRL language, themeaning of each line of code should be apparent based on the linguisticsthereof and/or on the attribute description chart that follows: SimpleDRL 48:    <LICENSE>    <DATA>    <NAME>Beastie Boy's Play</NAME>   <ID>39384</ID>    <DESCRIPTION>Play the song 3 times</DESCRIPTION>   <TERMS></TERMS>    <VALIDITY>    <NOTBEFORE>1998010223:20:14Z</NOTBEFORE>    <NOTAFTER>19980102 23:20:14Z</NOTAFTER>   </VALIDITY>    <ISSUEDDATE>19980102 23:20:14Z</ISSUEDDATE>   <LICENSORSITE>http://www.foo.com</LICENSORSITE>    <CONTENT>   <NAME>Beastie Boy's</NAME>    <ID>392</ID>    <KEYID>39292</KEYID>   <TYPE>MS Encrypted ASF 2.0</TTYPE>    </CONTENT>    <OWNER>   <ID>939KDKD393KD</ID>    <NAME>Universal</NAME>   <PUBLICKEY></PUBLICKEY>    </OWNER>    <LICENSEE>   <NAME>Arnold</NAME>    <ID>939KDKD393KD</ID>   <PUBLICKEY></PUBLICKEY>    </LICENSEE>    <PRINCIPAL TYPE==AND=>   <PRINCIPAL TYPE==OR=>    <PRINCIPAL>    <TYPE>x86Computer</TYPE>   <ID>3939292939d9e939</ID>    <NAME>Personal Computer</NAME>   <AUTHTYPE>Intel Authenticated Boot PC SHA-1 DSA512</AUTHTYPE>   <AUTHDATA>29293939</AUTHDATA>    </PRINCIPAL>    <PRINCIPAL>   <TYPE>Application</TYPE>    <ID>2939495939292</ID>    <NAME>Window=sMedia Player</NAME>    <AUTHTYPE>Authenticode SHA-1</AUTHTYPE>   <AUTHDATA>93939</AUTHDATA>    </PRINCIPAL>    </PRINCIPAL>   <PRINCIPAL>    <TYPE>Person</TYPE>    <ID>39299482010</ID>   <NAME>Arnold Blinn</NAME>    <AUTHTYPE>Authenticate user</AUTHTYPE>   <AUTHDATA>\\redmond\arnoldb</AUTHDATA>    </PRINCIPAL>   </PRINCIPAL>    <DRLTYPE>Simple</DRLTYPE>[the language tag 54]   <DRLDATA>    <START>19980102 23:20:14Z</START>    <END>1998010223:20:14Z</END>    <COUNT>3</COUNT>    <ACTION>PLAY</ACTION>   </DRLDATA>    <ENABLINGBITS>aaaabbbbccccdddd</ENABLINGBITS>   </DATA>    <SIGNATURE>    <SIGNERNAME>Universal</SIGNERNAME>   <SIGNERID>9382ABK3939DKD</SIGNERID>   <HASHALGORITHMID>MD5</HASHALGORITHMID>    <SIGNALGORITHMID>RSA128</SIGNALGORITHMID>    <SIGNATURE>xxxyyyxxxyyyxxxyyy</SIGNATURE>   <SIGNERPUBLICKEY></SIGNERPUBLICKEY>    <CONTENTSIGNEDSIGNERPUBLICKEY></CONTENTSIGNEDSIGNERPUBLICKEY>    </SIGNATURE>    </LICENSE> Script DRL48:    <LICENSE>    <DATA>    <NAME>Beastie Boy's Play</NAME>   <ID>39384</ID>    <DESCRIPTION>Play the song unlimited</DESCRIPTION>   <TERMS></TERMS>    <VALIDITY>    <NOTBEFORE>1998010223:20:14Z</NOTBEFORE>    <NOTAFTER>19980102 23:20:14Z</NOTAFTER>   </VALIDITY>    <ISSUEDDATE>19980102 23:20:14Z</ISSUEDDATE>   <LICENSORSITE>http://www.foo.com</LICENSORSITE>    <CONTENT>   <NAME>Beastie Boy's</NAME    <ID>392</ID>    <KEYID>39292</KEYID>   <TYPE>MS Encrypted ASF 2.0</TTYPE>    </CONTENT>    <OWNER>   <ID>939KDKD393KD</ID>    <NAME>Universal</NAME>   <PUBLICKEY></PUBLICKEY>    </OWNER>    <LICENSEE>   <NAME>Arnold</NAME>    <ID>939KDKD393KD</ID>   <PUBLICKEY></PUBLICKEY>    </LICENSEE>    <DRLTYPE>Script</DRLTYPE>[the language tag 54]    <DRLDATA>    function on_enable(action, args)as boolean    result = False    if action = “PLAY” then    result = True   end if    on_action = False    end function    ...    </DRLDATA>   </DATA>    <SIGNATURE>    <SIGNERNAME>Universal</SIGNERNAME>   <SIGNERID>9382</SIGNERID>    <SIGNERPUBLICKEY></SIGNERPUBLICKEY>   <HASHID>MD5</HASHID>    <SIGNID>RSA 128</SIGNID>   <SIGNATURE>xxxyyyxxxyyyxxxyyy</SIGNATURE>   <CONTENTSIGNEDSIGNERPUBLICKEY> </CONTENTSIGNEDSIGNERPUBLICKEY>   </SIGNATURE>    </LICENSE>

In the two DRLs 48 specified above, the attributes listed have thefollowing descriptions and data types: Attribute Description Data TypeId ID of the license GUID Name Name of the license String Content Id IDof the content GUID Content Key Id ID for the encryption key of the GUIDcontent Content Name Name of the content String Content Type Type of thecontent String Owner Id ID of the owner of the content GUID Owner NameName of the owner of the content String Owner Public Key Public key forowner of content. String This is a base-64 encoded public key for theowner of the content. Licensee Id Id of the person getting license. ItGUID may be null. Licensee Name Name of the person getting license.String It may be null. Licensee Public Key Public key of the licensee.This is String the base-64 encoded public key of the licensee. It may benull. Description Simple human readable description String of thelicense Terms Legal terms of the license. This String may be a pointerto a web page containing legal prose. Validity Not After Validity periodof license expiration Date Validity Not Before Validity period oflicense start Date Issued Date Date the license was issued Date DRL TypeType of the DRL. Example include String “SIMPLE” or “SCRIPT” DRL DataData specific to the DRL String Enabling Bits These are the bits thatenable String access to the actual content. The interpretation of thesebits is up to the application, but typically this will be the privatekey for decryption of the content. This data will be base- 64 encoded.Note that these bits are encrypted using the public key of theindividual machine. Signer Id ID of person signing license GUID SignerName Name of person signing license String Signer Public Key Public keyfor person signing String license. This is the base-64 encode public keyfor the signer. Content Signed Signer Public key for person signing theString Public Key license that has been signed by the content serverprivate key. The public key to verify this signature will be encryptedin the content. This is base-64 encoded. Hash Alg Id Algorithm used togenerate hash. String This is a string, such as “MD5”. Signature Alg IdAlgorithm used to generate String signature. This is a string, such as“RSA 128”. Signature Signature of the data. This is base- String 64encoded data.Methods

As was discussed above, it is preferable that any language engine 52 andany DRL language support at least a number of specific license questionsthat the digital license evaluator 36 expects to be answered by any DRL48. Recognizing such supported questions may include any questionswithout departing from the spirit and scope of the present invention,and consistent with the terminology employed in the two DRL 48 examplesabove, in one embodiment of the present invention, such supportedquestions or ‘methods’ include ‘access methods’, ‘DRL methods’, and‘enabling use methods’, as follows:

Access Methods

Access methods are used to query a DRL 48 for top-level attributes.

VARIANT QueryAttribute (BSTR key)

Valid keys include License.Name, License.Id, Content.Name, Content.Id,Content.Type, Owner.Name, Owner.Id, Owner.PublicKey, Licensee.Name,Licensee.Id, Licensee.PublicKey, Description, and Terms, each returninga BSTR variant; and Issued, Validity.Start and Validity.End, eachreturning a Date Variant.

DRL Methods

The implementation of the following DRL methods varies from DRL 48 toDRL 48. Many of the DRL methods contain a variant parameter labeled‘data’ which is intended for communicating more advanced informationwith a DRL 48. It is present largely for future expandability.

Boolean IsActivated(Variant data)

This method returns a Boolean indicating whether the DRL 48/ license 16is activated. An example of an activated license 16 is a limitedoperation license 16 that upon first play is active for only 48 hours.

Activate(Variant data)

This method is used to activate a license 16. Once a license 16 isactivated, it cannot be deactivated.

Variant QueryDRL(Variant data)

This method is used to communicate with a more advanced DRL 48. It islargely about future expandability of the DRL 48 feature set.

Variant GetExpires(BSTR action, Variant data)

This method returns the expiration date of a license 16 with regard tothe passed-in action. If the return value is NULL, the license 16 isassumed to never expire or does not yet have an expiration date becauseit hasn't been activated, or the like.

Variant GetCount(BSTR action, Variant data)

This method returns the number of operations of the passed-in actionthat are left. If NULL is returned, the operation can be performed anunlimited number of times.

Boolean IsEnabled(BSTR action, Variant data)

This method indicates whether the license 16 supports the requestedaction at the present time.

Boolean IsSunk(BSTR action, Variant data)

This method indicates whether the license 16 has been paid for. Alicense 16 that is paid for up front would return TRUE, while a license16 that is not paid for up front, such as a license 16 that collectspayments as it is used, would return FALSE.

Enabling Use Methods

These methods are employed to enable a license 16 for use in decryptingcontent.

Boolean Validate (BSTR key)

This method is used to validate a license 16. The passed-in key is theblack box 30 public key (PU-BB) encrypted by the decryption key (KD) forthe corresponding digital content 12 (i.e.,( KD(PU-BB))) for use invalidation of the signature of the license 16. A return value of TRUEindicates that the license 16 is valid. A return value of FALSEindicates invalid.

int OpenLicense 16(BSTR action, BSTR key, Variant data)

This method is used to get ready to access the decrypted enabling bits.The passed-in key is ( KD(PU-BB)) as described above. A return value of0 indicates success. Other return values can be defined.

BSTR GetDecryptedEnablingBits (BSTR action, Variant data)

Variant GetDecryptedEnablingBitsAsBinary (BSTR action, Variant Data)

These methods are used to access the enabling bits in decrypted form. Ifthis is not successful for any of a number of reasons, a null string ornull variant is returned.

void CloseLicense (BSTR action, Variant data)

This method is used to unlock access to the enabling bits for performingthe passed-in action. If this is not successful for any of a number ofreasons, a null string is returned.

Heuristics

As was discussed above, if multiple licenses 16 are present for the samepiece of digital content 12, one of the licenses 16 must be chosen forfurther use. Using the above methods, the following heuristics could beimplemented to make such choice. In particular, to perform an action(say ‘PLAY’) on a piece of digital content 12, the following steps couldbe performed:

1. Get all licenses 16 that apply to the particular piece of digitalcontent 12.

2. Eliminate each license 16 that does not enable the action by callingthe IsEnabled function on such license 16.

3. Eliminate each license 16 that is not active by calling IsActivatedon such license 16.

4. Eliminate each license 16 that is not paid for up front by callingIsSunk on such license 16.

5. If any license 16 is left, use it. Use an unlimited-number-of-playslicense 16 before using a limited-number-of-plays license 16, especiallyif the unlimited-number-of-plays license 16 has an expiration date. Atany time, the user should be allowed to select a specific license 16that has already been acquired, even if the choice is notcost-effective. Accordingly, the user can select a license 16 based oncriteria that are perhaps not apparent to the DRM system 32.

6. If there are no licenses 16 left, return status so indicating. Theuser would then be given the option of:

using a license 16 that is not paid for up front, if available;

activating a license 16, if available; and/or

performing license acquisition from a license server 24.

Secure DRM Processor Architecture

Referring now to FIG. 13, it is to be appreciated that in one mode ofobtaining and rendering digital content 12, such digital content 12 isdownloaded or otherwise placed on a personal computer 60 or the like,and the corresponding digital license 16 once obtained is alsodownloaded or otherwise placed on the personal computer 60 or the like.Thereafter, the content 12 and the license 16 (or a sub-license basedthereon) are downloaded from the computer 60 to a portable computingdevice 62. For example, the portable device 62 may be a portable audioor multimedia player such as the DIAMOND RIO portable player, marketedby S3 Incorporated of Santa Clara, Calif. Notably, such two-steptransfer of the content 12 is not essential to the present invention.Accordingly, for the purpose of the present invention, the content 12may come from an arbitrary source.

Designing and configuring a portable device 62 to support the DRMarchitecture as set forth above raises several issues. At least some ofsuch issues are dealt with in U.S. patent application Ser. No.09/______, entitled “Binding a Digital License to a Portable Device orthe Like in a Digital Rights Management (DRM) System and CheckingOut/Checking In the Digital License to/from the Portable Device or theLike” and filed concurrently herewith under Attorney Docket No.MSFT-310/164266.1, hereby incorporated by reference herein in itsentirety.

As was pointed out in such application, all obtaining of digital content12 and a corresponding digital license or sub-license (hereinafter‘license’) 16 for the portable device 62 is performed by way of acomputer 60 or the like. Thus, the portable device 62 and the DRM system32 p (FIG. 13) therein need not include such functionality therein,except insofar as is necessary to download the content 12 and thelicense 16. Accordingly, significant license acquisition and contentacquisition portions of the DRM system 32 as resident on the computer 60may be omitted from the DRM system 32 p as resident on the portabledevice 62.

As was also pointed out, the portable device 62 may be defined as agenerally closed device in that data can be on-loaded and off-loadedonly in a limited manner, user access to hardware within the portabledevice 62 is very limited, and input and display functionality islimited to a few function keys and perhaps a small LCD screen,respectively. Thus, a content thief can do very little in the way ofexamining either the memory or physical contents of the portable device62 to obtain content 12 therein in an unencrypted form or decryptionkeys. In contrast, the computer 60 may be defined as a generally opendevice in that data can be on-loaded and off-loaded in a wide-rangingmanner by any of a broad range of hardware and/or software, user accessto hardware within the portable device 62 is not limited in anysignificant way, and input and display functionality is available by wayof a full-function keyboard, a mouse, a high-resolution monitor, and thelike. Thus, a content thief has many potential opportunities availableto examine the memory and physical contents of the computer 60 to obtaincontent 12 therein in an unencrypted form or decryption keys. In sum,then, the portable device 62 as a closed device is less susceptible tonefarious actions committed by a content thief, especially as comparedto the computer 60 as an open device.

As a result, and also importantly, the portable device 62 and the DRMsystem 32 p therein need not include functionality therein necessary toguard against most types of content theft and decryption key theft,except insofar as is necessary during download of the content 12 and thesub-license 16. Accordingly, significant theft prevention portions ofthe DRM system 32 as resident on the computer 60 may be omitted from theDRM system 32 p as resident on the portable device 62 for the reasonthat functions such as hiding secrets, protecting integrity, isolatingmemory, and the like, while still necessary, are provided by thehardware mechanisms, which make the portable device a closed device. Incontrast, on an open device such functions are typicallyimplemented/approximated/simulated by means of softwaretamper-resistance.

To sum up, then, the DRM system 32 p as resident on the portable device62 need only include functionality necessary (1) to authenticate theportable device 62 to the computer 60 during downloading of asub-license 16 s to the portable device and at other appropriate times,and to facilitate such downloading, and (2) to render content 12 on theportable device 62 according to downloaded and resident license(s) 16,including ensuring that requirements in a license 16 are filled andobtaining the content key (KD) from the license 16. All otherfunctionality as available in the DRM system 32 on the computer 60 iseither unnecessary in the DRM system 32 p on the portable device 62, oris inherent in the portable device 62 being a closed device.

However, and importantly, such other functionality is either unnecessaryor inherent as discussed above only if the portable device 62 andspecifically the processor 64 thereon can be trusted. That is to say,the portable device 62 and the processor 64 thereon must be of a typethat substantially completely prevents a content thief from performingnefarious acts that would allow obtaining of content 12 therein in anunencrypted form or decryption keys. Accordingly, in one embodiment ofthe present invention, the processor 64 is a secure processor having anarchitecture as disclosed below. In particular, in one embodiment of thepresent invention, the secure processor 64 is constructed to run onlyauthorized code. Note that the secure processor 64 and the architecturethereof of the present invention, though particularly applicable to aportable device 62, are not limited to such portable device 62. Instead,such secure processor 64 and architecture thereof may be employed in anytype of computing device 14 without departing from the spirit and scopeof the present invention.

In addition to running authorize code only, the secure processor 64 ofthe present invention ensures data privacy in that data on the portabledevice 62 associated with a particular application on the device 62 canbe kept secret from any other application on the device 62. Such datamay be any data, and for example may include passwords, account numbers,private cryptographic keys, financial or other private data, and othersensitive personal information. Generally, in the present invention, thesecurity processor 64 is operated to maintains a strict cryptographicseparation between applications operating systems.

In the present invention, generally, the security of the processor 64 isbased on the use of a security kernel 68 in the processor 64. Suchsecurity kernel 68 provides relevant higher-level functionalityincluding protection from hostile code (e.g. a virus), authentication toa remote host (e.g. a DRM license server 24), certification of upgrades,and piracy protection for software on the portable device 62.

In the present invention, the secure processor 64 is constructed toinclude a security (CPU) key 66 physically hard-wired (permanentlystored) thereinto, and the security kernel 68 is also physicallyhard-wired thereinto, where only the security kernel 68 can access theCPU key 66. Such physical hard-wiring may be performed duringmanufacturing of the secure processor 64 and may be done in anyappropriate manner without departing from the spirit and scope of thepresent invention. Such physical hardwiring is known or should beapparent to the relevant public and therefore need not be describedherein in any detail. For example, the secure processor 64 may bemanufactured with storage space 70 for a CPU key 66 and a securitykernel 68, where the storage space 70 is in the form of ROM to bepre-programmed by the manufacturer. Such ROM may comprise, at least inpart, fused memory locations. Thus, as a final manufacturing step,selected ones of the fused memory locations in the storage space 70 are‘blown’ to permanently instantiate a particular CPU key 66 and aparticular security kernel 68.

In the present invention, the secure processor 64 is operable in anormal mode and a preferred mode, where the security kernel 68 canaccess the CPU key 66 only during the preferred mode. For example, theprocessor 64 may be manufactured with a physical switch (such as anelectronic gate) that allows the CPU key 66 to be read only when theprocessor 64 is in preferred mode. As may be appreciated, the securitykernel 68 employs the accessed CPU key 66 during the preferred mode toinstantiate and/or authenticate a secure application 72 such as a DRMsystem 32 p, a banking/financial system, etc. on the portable device 62.The security kernel 68 may automatically instantiate a particular secureapplication, may authenticate a secure application instantiated byanother process, or may initially instantiate a secure chooserapplication 72 c that allows a user to select from one or more availablesecure applications 72 on the portable device 62.

In any case, the accessed CPU key 66 is employed by the security kernel68 to decrypt one or more encrypted security keys for the application 72instantiated. For example, in the case where the security kernel 68instantiates/authenticates the DRM system 32 p on the portable device62, it may be that at least the black box private key PR-BB for the DRMsystem 32 p is already encrypted according to the CPU key 68 and storedon the portable device 62 as CPU(PR-BB), and the security kernel duringthe preferred mode employs the accessed CPU key 66 to decrypt CPU(PR-BB)to produce (PR-BB) such that (PR-BB) is available to the instantiatedDRM system 32 p. Such CPU key 66 may also encrypt one or more nintermediate keys which in turn encrypt (PR-BB), as seen below. As maybe appreciated, then, the CPU key 66 is the key to unlocking or decryptthe secrets identified with each application 72, and therefore must bewell-protected.

In the present invention, then, the security kernel 68 ensures that eachapplication 72 has access to the secrets of such application 72, anddoes not have access to the secrets of any other application 72. As aresult, each application 72 on the portable device 62 is isolated fromevery other application 72 on the portable device 62. Such functionalityis required for banking applications (credit card numbers, PINs, e.g.)and DRM applications (private keys, e.g.).

In addition, the accessed CPU key 66 and/or the decrypted key(s) may beemployed by the security kernel 68 to authenticate/verify theapplication 72 to be instantiated. In particular, the application 72 mayinclude a certificate or the like, and the security kernel 72 mayperform a hash or MAC (message authentication code) over the code forthe application based on the CPU key 66 and then compare the hash or MACto the certificate or the like. Details of the hash depend on whetherpublic-key (asymmetric) or symmetric cryptography is employed, asdiscussed in more detail below. As may be appreciated, any appropriatehash function may be employed without departing from the spirit andscope of the present invention. Hash functions are generally known orshould be appreciated by the relevant public and therefore need not bedescribed herein in any detail.

If the compare fails, the security kernel 72 may refuse toinstantiate/authenticate the application 72 or may instantiate or allowinstantiation but not decrypt the secrets for the application 72, forexample. As may be appreciated, by having the security kernel 68authenticate/verify an application 72 based on a performed hash, thesecurity kernel 68 ensures that system resources on the portable device62 (in particular, the application-specific secrets) are restricted toan authorized application 72.

In one embodiment of the present invention, and referring now to FIG.14, the security processor 64 enters preferred mode whenever apredefined initializing processor action is performed. For example, thesecurity processor 64 may enter preferred mode whenever a CPU reset isperformed, thus making the CPU key 66 accessible by the security kernel68 (step 1401). As may be appreciated, a CPU reset is a typicalprocessor operation that places a processor in an initialized statewithout necessarily erasing all memory on the processor 62. As may beappreciated, such attribute is desirable in instances where certain datafrom prior to a CPU reset is necessary after such CPU reset.

The CPU reset may preferably be performed either manually such as atinitial power-up of the processor 64, or programmatically such as byprogram code running on the processor 64. In one embodiment of thepresent invention, upon the CPU reset, data in cache 74 on the processor64 is erased (step 1403). Thus, any data previously stored in the cache74 is not available during preferred mode to interfere with preferredmode processes, and in particular any data previously stored in thecache 74 cannot be employed to get at the CPU key 66 or subvert theexecution of the security kernel 68. With such erasure, then, a contentor data thief intending to perform a nefarious act such as identifyingthe CPU key 66 during preferred mode cannot place a malicious program incache 74, enter preferred mode, and expect to run the malicious programduring preferred mode. Quite simply, the malicious program is erased aspart of erasing the cache 74.

Once the cache is erased, the security kernel 68 is then run (step1405). As may be appreciated, the security kernel 68 is run by loadingsame from the storage space 70 onto the processor 64 and then performingthe program code incumbent in such security kernel 68. Typically, thestorage space 70 with regard to the security kernel 68 is processor ROMand not some secondary storage medium such as a hard disk, or flashmemory, although the present invention is not restricted in this regard.

Generally, the program code of the security kernel 68 as performedaccesses the CPU key 66 at a predetermined memory location in thestorage space 70 (step 1407), and then applies the accessed CPU key 66to decrypt the one or more encrypted security keys for the applicationto be instantiated (step 1409), as was discussed above. Presumably, suchkey(s) have already been encrypted according to the CPU key 68 andstored in the storage space 70. Thereafter, the program code of thesecurity kernel 68 stores the decrypted key(s) on the portable device 62in a location where the application to be instantiated expects thekey(s) to be found (step 1410).

In addition, the program code of the security kernel 68 instantiates,causes instantiation or allows the instantiation of the application onthe portable device 62 (step 1413). Performing such instantiation, isgenerally known or should be apparent to the relevant public andtherefore need not be described herein in any detail. Accordingly, anyparticular form of instantiation maybe performed without departing fromthe spirit and scope of the present invention. Such instantiation orloading comprises placing executable code and data into a memory space,such that the code can be executed. In principle, this can be a complextask and may involve things, such a resolving dependencies (by loadingother DLLs) or relocation (changing certain addresses in the code).Notably, loading in itself is not critical to security and does notnecessarily have to be performed by the security kernel 68. The criticaltask for the security kernel 68 is instead authentication of the loadedimage. That is, the security kernel 68 has to ensure that the result ofthe loading (or instantiation) is what it claims to be.

As mentioned above, the application 72 to be instantiated may beauthenticated/verified according to the CPU key 68 and/or the decryptedkey(s) (step 1411). In such case, prior to or after instantiation, theprogram code of the security kernel 68 employs the accessed CPU key 66and/or the decrypted key(s) to perform a hash or MAC over the code forthe application 72 to be instantiated and then compares the hash or MACto a certificate or the like accompanying the application 72. If thecompare fails, the security kernel 72 may refuse to instantiate theapplication 72 or may instantiate but not decrypt the secrets for theapplication 72 as at step 1409. If the secrets are already decrypted,the security kernel 72 may decide to delete the decrypted secrets.

Once the security kernel finishes instantiating/authenticating theapplication, the processor 64 enters normal mode and the CPU key 66becomes inaccessible (step 1415). Entering normal mode may occurautomatically upon the security kernel 68 finishing or may occur by aninstruction in the security kernel 68.

In one embodiment of the present invention, upon entering normal mode,data in the cache 74 on the processor 64 is once again erased (step1417). Thus, any sensitive data in the cache 74 from preferred modeoperations, such as for example the CPU key 66 or a secret for anapplication 72 as derived from the CPU key 66, is not available duringnormal mode to be read by a content or data thief. Note that erasingcache 74 both at steps 1403 and 1417 may also encompass zeroingregisters and writing zero or random values to memory locations thatcontain information derived from the CPU key. Note that both the memorylocations themselves and any transient copies must be erased.

Referring now to FIG. 15, it is seen that in the case where the securitykernel 68 initially instantiates/authenticates a secure chooserapplication 72 c that allows a user to select from one or more availablesecure applications 72 on the portable device 62, the security kernel 68employs such chooser application 72 c and a stored chooser value 76 thatis persistent and that is accessible to the security kernel 68 to selectfrom among at least one other application 72 available on the portabledevice 62. Importantly, each time the processor 64 enters the preferredmode and runs the security kernel 68, such security kernel 68 checks thechooser value 76 and instantiates/authenticates a particular application72, 72 c corresponding to the chooser value. For example, if the chooservalue 76 is set to 0, the security kernel 68 instantiates/authenticatesthe chooser application 72 c. Similarly, if the chooser value 76 is setto 1, 2, or 3, the security kernel 68 instantiates/authenticates afirst, second, or third application 72, respectively.

In employing the chooser application 72 c and the chooser value 76, itis seen that upon initial power-up of the processor 64, the chooservalue 76 is set to the value corresponding to the chooser application 72c (0 in the above example) (step 1501). Thus, upon a power-up CPU reset,the processor 64 enters the preferred mode and runs the security kernel68, the security kernel checks the chooser value 76 and finds it to be0, and the security kernel 68 instantiates/authenticates thecorresponding chooser application 72 c (steps 1503,1505). Thereafter,the processor 64 enters the normal mode and the instantiated chooserapplication 72 c is left to run on the portable device 62 (step 1507).As may be appreciated, the chooser application 72 c presents a number ofapplications 72 for selection by a user of the portable device 62, andthe user thus selects one of the presented applications 72 to beinstantiated on the portable device 62 (step 1509). Note that thepresentation of the applications 72 to the user may be done in anyappropriate manner without departing from the spirit and scope of thepresent invention. For example, the portable device 62 may present theapplications 72 on a display (not shown) on the portable device 62, orthe applications may be hard-wired into labeled selection buttons (notshown) on the portable device 62.

Upon user selection of an application 72 to be instantiated, the chooserapplication 72 c sets the chooser value 76 to the value corresponding tothe selected application 72 (1, e.g.) (step 1511), and executes a CPUreset (step 1513). Importantly, the chooser value 76 is persistent inthat the chooser value 76 is not erased by the CPU reset. That is, thechooser value 76 is preferably stored in a memory location not affectedby a CPU reset so as to be available after the CPU reset.

As may now be appreciated, after the CPU reset is executed by thechooser application 72 c, the processor 64 enters the preferred mode andruns the security kernel 68, the security kernel checks the chooservalue 76 and finds it to be 1, and the security kernel 68instantiates/authenticates the corresponding chosen application 72(steps 1515, 1517). Thereafter, the processor 64 enters the normal modeand the instantiated chosen application 72 c is left to run on theportable device 62 (step 1519).

In one embodiment of the present invention, upon the selectedapplication 72 being instantiated and run by the security kernel 68,either the security kernel 68 (prior to the processor entering normalmode) or the chosen application 72 (after the processor enters normalmode) sets the chooser value 76 back to the value corresponding to thechooser application 72 (0 in the present example) (step 1521). Thus,upon execution of another CPU reset (step 1523) from whatever source,the security kernel 68 once again instantiates/authenticates the chooserapplication 72 c to begin the selection process anew. Once again, thechooser value 76, being persistent, is not erased by the CPU reset andis available after the CPU reset.

Notably, the chooser value 76 does not have to be an integer. Inprinciple, the chooser value 76 could be the entire instantiated(loaded) image or program. In this case, the last running program loadsthe next program and then sets off the special CPU instruction, whichtriggers preferred mode.

Secure DRM Processor—Symmetric Cryptography and the Code Image

In one embodiment of the present invention, and as alluded to above, thesecurity kernel 68 does not have public key/private key encryption anddecryption capabilities. Instead, the security kernel 68 implements aMAC (message authentication code) and a symmetric cipher, and the CPUkey 66 is therefore a symmetric key. In such embodiment, and referringnow to FIG. 16, each application 72 on the portable device 62 exists inthe form of a corresponding code image 78 that is constituted at leastin part to facilitate symmetric encryption and decryption.

To constitute the code image 78, and in one embodiment of the presentinvention, there is a manufacturer-specific device key KMAN which isunique to each portable device 62 but independent of the CPU key 66. Thepurpose of KMAN is to allow each device manufacturer to administrate itsdevice secrets independently. In particular, and as will be seen, KMANfrees the manufacturer of the processor 64 from the burden ofmaintaining a secret database associated with each manufacturedprocessor 64.

With KMAN, each code image 78 for the portable device 62 has a header 80and a main body 82. In particular, the header 80 has the following form,where KCPU is the CPU key 66 and KCODE is the key secret of thecorresponding application 72: KCPU (KMAN) KMAN encrypted according toKCPU MAC (main body 82, KMAN) message authentication code of the mainbody 82 under KMAN KMAN (KCODE) KCODE encrypted according to KMANNote that the MAC may also be based on KMAN(KCODE).

When called to load a given code image 78, and referring now to FIG. 17,the security kernel 68 performs the following steps related to theheader 80 of the code image 78:

-   -   1. Apply KCPU to KCPU (KMAN) to produce KMAN (step 1701);    -   2. Compute MAC (main body 82, KMAN) (step 1703);    -   3. Compare computed MAC (main body 82, KMAN) to MAC (main body        82, KMAN) from the header 80 to determine if the code image 78        has been corrupted, modified, adulterated, etc. (step 1705); and    -   4. Assuming the MACs match, Apply KMAN to KMAN (KCODE) to        produce KCODE (step 1707).

As may be appreciated, the manufacturer of the portable device 62 musthave access to the CPU key 66 (KCPU) to generate the header 80 of thecode image 78. However, such CPU key 66 is never revealed outside theprocessor 64. In one embodiment of the present invention, this apparentcontradiction is resolved by providing the processor 64 with a third,production mode during which the CPU key 66 is externally accessible tothe manufacturer of the portable device 62.

In such embodiment, and referring now to FIG. 18, the processor 64 ismanufactured and shipped to the manufacturer of the portable device 62in production mode (step 1801), and the manufacturer of the portabledevice 62 accesses the CPU key 66 of the processor 64 in production mode(step 1803). Such manufacturer then generates the header 80 for eachcode image 78 for the processor 64/portable device 62 based on theaccessed CPU key 66 (KCPU), KMAN, and the main body 82 (step 1805).

Importantly, at some point prior to shipping the portable device 62 to aconsumer or to be purchased by a consumer, the manufacturer of theportable device 62 permanently disables production mode for theprocessor 64 within the portable device (step 1807). Thus, such consumercannot actuate such production mode to access the CPU key 66. Note thatpermanent disablement of production mode for the processor 64 may beperformed prior to or after loading code images 78 (step 1809) onto theportable device 62 that are generated based on the accessed CPU key 66.

Permanently disabling such production mode may be done in anyappropriate manner without departing from the spirit and scope of thepresent invention. For example, the processor 64 may be constructed witha fuse 84 (FIG. 13) or the like, and the fuse 13 may be ‘blown’ topermanently disable production mode. Such permanent disabling is knownor should be apparent to the relevant public and therefore need not bedescribed herein in any detail.

Secure DRM Processor—Asymmetric Cryptography and the Code Image

In one embodiment of the present invention, and as also alluded toabove, the security kernel 68 does have public key/private keyencryption and decryption capabilities. Here, the security kernel 68implements a hash and public-key operations (encryption, decryption,signing, signature verification), and the CPU key 66 is therefore theprivate key of a public key-private key pair. In such embodiment, andreferring now to FIG. 19, each application 72 on the portable device 62exists in the form of a corresponding code image 78 that is constitutedat least in part to facilitate asymmetric encryption and decryption.

To constitute the code image 78 in this instance, and in one embodimentof the present invention, only the CPU key 66 (private key) need beemployed rather than such CPU key 66 and the aforementionedmanufacturer-specific device key KMAN. As may be appreciated, this isbecause the CPU key 66 is a private key and a separate correspondingpublic key is employed by the external world. Put another way, and asshould be appreciated, the asymmetric nature of the internal or privateCPU key 66 and the corresponding external or public key imparts suchkeys with the functionality necessary to perform all encryption withoutany other keys.

In one embodiment of the present embodiment, each code image 78 for theportable device 62 still has a header 80 and a main body 82. However,with the public key-private key pair including the CPU key 66 as theprivate key thereof, and without the need for KMAN as above, the header80 has the following simplified form, where KCPU is the CPU key 66 andKCODE is the key secret of the corresponding application 72: public key(HASH (main body Hash of the main body 82 and KCODE, 82), KCODE) bothencrypted according to the public key

Importantly, in both the symmetric case above and the asymmetric casehere, only the security kernel 68 can get to KCODE, inasmuch as only thesecurity kernel 68 can access the private key (CPU key 66) correspondingto the public key, as was discussed above. Also importantly, since onlythe security kernel 68 can access the private key (CPU key 66)corresponding to the public key, KCODE is tied to the security kernel68, the CPU key 66, and the portable device 62. As tied, and as shouldbe appreciated, KCODE cannot be transferred over to another portabledevice 62/security kernel 68 and be employed thereon.

Also importantly, KCODE is tied to the executable image 78 to which itbelongs. Assuming that different images 78/programs on the device 62 donot trust each other, KCODE for one image 78 should not be accessible byany entity other than the application instantiated from such image.Thus, the image 78 of an application to be instantiated should only beable to access its KCODE if it is unadulterated and unmodified, as shownby a hash comparison. If only a single bit in the image 78 has beenchanged, the image 78 is not to be trusted and should not be able toaccess its KCODE.

Thus, when called to load a given code image 78, and referring now toFIG. 20, the security kernel 68 performs the following steps related tothe header 80 of the code image 78:

-   -   1. Compute HASH (main body 82) (step 2001);    -   2. Apply private key to public key (HASH (main body 82), KCODE)        to produce HASH (main body 82) and KCODE (step 2003);    -   3. Compare computed HASH to decrypted HASH to determine if the        code image 78 has been corrupted, modified, adulterated, etc.        (step 2005); and    -   4. Assuming the HASHs match, employing the decrypted KCODE as        appropriate (step 2007).        As may be appreciated, steps 2001-2007 more generally        instantiate the functions of (1) verifying that the header 80        with KCODE therein belongs to the code image 78 and (2) exposing        KCODE to the security kernel 68.

Of course, any other mechanism, symmetric or asymmetric, for tying KCODEto a security kernel 68 and to its code image 78 and limiting access toKCODE to the security kernel 68 and its code image 78 may be employedwithout departing from the spirit and scope of the present invention. Asbut one example, the header 80 may have the following simplified form:public key (HASH (main body 82, Hash of both the main body 82 and KCODE)KCODE, encrypted according to the public key public key (KCODE) KCODE,encrypted according to the public keyOf course, such header 80 requires two decryptions rather than one, asabove.

As may be appreciated, use of an asymmetric public key-private key pairfrees the manufacturer of the portable device 62 from having to accessthe CPU key 66 to generate the header 80 of the code image 78. Thus,such CPU key 66 truly never need be revealed outside the processor 64,and no production mode need be provided to the processor 64, as is thecase above with regard to using a symmetric key as the CPU key 66.

With use of an asymmetric key pair, then, certified code images 78 maybe produced without requiring special production modes or secretdatabases. The manufacturer of the portable device 62 simply uses thepublic-key corresponding to the CPU key 66 as a private key to producethe required header 80 for each code image 78. In fact, if the publickey is indeed public, anybody can produce a code image 78 with a validheader 80.

Secure DRM Processor—Asymmetric and Symmetric Cryptography

Fast public key-private key cryptography code may require 10 to 20kilobytes of memory space, which may be expensive for on-chip ROM or thelike in a portable device 62. Thus, in one embodiment of the presentinvention, and referring now to FIG. 21, the security kernel 68 is acode security kernel 68 c which uses symmetric cryptography as describedabove, but only on a privileged code image 78 which implements anextended version of the security kernel 68 e. The extended securitykernel 68 e in turn uses the public key-private key asymmetriccryptography as described above. Such extended security kernel 68 e,then, is employed to load an arbitrary application 72 from acorresponding code image 78.

Conclusion

Notably, with a portable device 62 having a secure processor 64 andsecure kernel 68 as disclosed above, protection of the security keys andother secrets is relegated from a black box -type device to theplatform. Thus, the platform assures that an application gets a secretthat is determined by the entirety of the running software stack. Alicense server 24 or sub-licensing process receiving a request from theplatform sees a component with a certified key. The certificationindicates that the key could only have come from a trusted devicerunning a known software configuration. Hence the server 24 or processtrusts the platform and issues the license 16/sub-license 16 s. In amore generalized e-commerce case, a vendor receiving a request (to buy aproduct, to trade a stock, etc.) checks that the request is coming froma trusted device running a known software stack. The check succeedsbecause the certified key would only have been disclosed if the softwarestack was certified trusted, so the transaction is allowed.

The programming necessary to effectuate the processes performed inconnection with the present invention is relatively straight-forward andshould be apparent to the relevant programming public. Accordingly, suchprogramming is not attached hereto. Any particular programming, then,may be employed to effectuate the present invention without departingfrom the spirit and scope thereof.

In the foregoing description, it can be seen that the present inventioncomprises a new and useful secure processor 64 and an architecturetherefor that can be trusted to keep hidden a secret of the DRM system32, especially in cases where the processor 64 is on a portable device62 or the like. It should be appreciated that changes could be made tothe embodiments described above without departing from the inventiveconcepts thereof. For example, although disclosed as being particularlyrelevant to a DRM system 32 on a portable device 62, the invention mayalso be employed on another system such as for example a banking systemand/or may also be employed on a device other than a portable device 62without departing from the spirit and scope of the present invention. Itshould be understood, therefore, that this invention is not limited tothe particular embodiments disclosed, but it is intended to covermodifications within the spirit and scope of the present invention asdefined by the appended claims.

1. A secure processor for a computing device, the processor beingoperable in a normal mode and a preferred mode, the processor includinga security kernel for being instantiated on the processor when theprocessor enters into the preferred mode and a security key accessibleby the instantiated security kernel when the processor is operating inthe preferred mode, the security kernel employing the accessed securitykey during the preferred mode to authenticate a secure application onthe computing device, wherein the security kernel allows the processorto be trusted to keep hidden a secret of the application.
 2. Theprocessor of claim 1 in combination with the application.
 3. Theprocessor of claim 2 wherein the application is selected from a groupconsisting of a digital rights management (DRM) system and abanking/financial system.
 4. The processor of claim 1 wherein thesecurity kernel automatically authenticates a particular application. 5.The processor of claim 1 wherein the security kernel initiallyauthenticates a chooser application that allows a user to select from atleast one available applications on the computing device.
 6. Theprocessor of claim 1 wherein the security kernel employs the accessedsecurity key during the preferred mode to decrypt at least one encryptedkey for the application.
 7. The processor of claim 1 in combination withthe computing device.
 8. The processor of claim 7 wherein the computingdevice is a portable computing device.
 9. The processor of claim 1further comprising a storage space, the security kernel beingpermanently stored in the storage space.
 10. The processor of claim 1further comprising a storage space, the security key being permanentlystored in the storage space.
 11. The processor of claim 1 wherein thesecurity kernel employs the accessed security key during the preferredmode to authenticate/verify the application prior to instantiationthereof.
 12. The processor of claim 11 wherein the security kernelperforms a hash/MAC (message authentication code) over at least aportion of the application and then compares the hash/MAC to a hash/MACcorresponding to the application.
 13. The processor of claim 1 whereinsuch processor enters preferred mode whenever a predefined initializingprocessor action is performed.
 14. The processor of claim 13 whereinsuch processor enters preferred mode whenever a CPU reset is performed.15. A method for a secure processor to instantiate a secure applicationthereon, the method comprising: instantiating a first security kernelwhich employs symmetric cryptography; instantiating by way of theinstantiated first security kernel a second security kernel whichemploys asymmetric cryptography; and authenticating by way of theinstantiated second security kernel the secure application.
 16. Themethod of claim 15 wherein the security key of the processor is asymmetric key and the second security kernel is instantiated by thefirst security kernel from a code image including a main body and aheader including: KCPU (KMAN) KMAN encrypted according to KCPU KMAN(KCODE) KCODE encrypted according to KMAN

where KCPU is a security key of the processor, KMAN is a device keyindependent of the security key, and KCODE is the private key of thesecond security kernel, and wherein the first security kernel appliesthe security key to decrypt the private key of the second securitykernel during instantiation thereof by: applying KCPU to KCPU (KMAN) toproduce KMAN; and applying KMAN to KMAN (KCODE) to produce KCODE. 17.The method of claim 15 wherein the application is instantiated by thesecond security kernel from a code image including a main body and aheader including: public key (KCODE) KCODE encrypted according to thepublic key

where KCODE is the secret of the application, and wherein the secondsecurity kernel applies the private key to decrypt the secret of theapplication during authentication thereof.
 18. A computer-readablemedium having stored thereon computer-executable instructionsimplementing a method for a secure processor to instantiate a secureapplication thereon, the method comprising: instantiating a firstsecurity kernel which employs symmetric cryptography; instantiating byway of the instantiated first security kernel a second security kernelwhich employs asymmetric cryptography; and authenticating by way of theinstantiated second security kernel the secure application.
 19. Themedium of claim 18 wherein the security key of the processor is asymmetric key and the second security kernel is instantiated by thefirst security kernel from a code image including a main body and aheader including: KCPU (KMAN) KMAN encrypted according to KCPU KMAN(KCODE) KCODE encrypted according to KMAN

where KCPU is a security key of the processor, KMAN is a device keyindependent of the security key, and KCODE is the private key of thesecond security kernel, and wherein the first security kernel appliesthe security key to decrypt the private key of the second securitykernel during instantiation thereof by: applying KCPU to KCPU (KMAN) toproduce KMAN; and applying KMAN to KMAN (KCODE) to produce KCODE. 20.The medium of claim 18 wherein the application is instantiated by thesecond security kernel from a code image including a main body and aheader including: public key (KCODE) KCODE encrypted according to thepublic key

where KCODE is the secret of the application, and wherein the secondsecurity kernel applies the private key to decrypt the secret of theapplication during instantiation thereof.